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class="sidebar-actions"><section class="sidebar-filter-container"><div class="sidebar-filter "><label id="sidebar-filter-label" class="sidebar-filter-label" for="sidebar-filter-input"><span class="icon icon-filter"></span><span class="visually-hidden">Filter sidebar</span></label><input id="sidebar-filter-input" autoComplete="off" class="sidebar-filter-input-field false" type="text" placeholder="Filter" value=""/><button type="button" class="button action has-icon clear-sidebar-filter-button"><span class="button-wrap"><span class="icon icon-cancel "></span><span class="visually-hidden">Clear filter input</span></span></button></div></section></header><div class="sidebar-inner-nav"><div class="in-nav-toc"><div class="document-toc-container"><section class="document-toc"><header><h2 class="document-toc-heading">In this article</h2></header><ul class="document-toc-list"><li class="document-toc-item "><a class="document-toc-link" href="#try_it">Try it</a></li><li class="document-toc-item "><a class="document-toc-link" href="#syntax">Syntax</a></li><li class="document-toc-item "><a class="document-toc-link" href="#description">Description</a></li><li class="document-toc-item "><a class="document-toc-link" href="#examples">Examples</a></li><li class="document-toc-item "><a class="document-toc-link" href="#specifications">Specifications</a></li><li class="document-toc-item "><a class="document-toc-link" href="#browser_compatibility">Browser compatibility</a></li><li class="document-toc-item "><a class="document-toc-link" href="#see_also">See also</a></li></ul></section></div></div><div class="sidebar-body"><ol><li class="section"><a href="/en-US/docs/Web/JavaScript">JavaScript</a></li><li class="section">Tutorials and guides</li><li class="toggle"><details><summary>Beginner's tutorials</summary><ol><li><a href="/en-US/docs/Learn_web_development/Getting_started/Your_first_website/Adding_interactivity">Your first website: Adding interactivity</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting">Dynamic scripting with JavaScript</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries">JavaScript frameworks and libraries</a></li></ol></details></li><li class="toggle"><details><summary>JavaScript Guide</summary><ol><li><a href="/en-US/docs/Web/JavaScript/Guide/Introduction">Introduction</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Grammar_and_types">Grammar and types</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Control_flow_and_error_handling">Control flow and error handling</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Loops_and_iteration">Loops and iteration</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Functions">Functions</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Expressions_and_operators">Expressions and operators</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Numbers_and_strings">Numbers and strings</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Representing_dates_times">Representing dates & times</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Regular_expressions">Regular expressions</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Indexed_collections">Indexed collections</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Keyed_collections">Keyed collections</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Working_with_objects">Working with objects</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Using_classes">Using classes</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Using_promises">Using promises</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Typed_arrays">JavaScript typed arrays</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Iterators_and_generators">Iterators and generators</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Internationalization">Internationalization</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Meta_programming">Meta programming</a></li><li><a href="/en-US/docs/Web/JavaScript/Guide/Modules">JavaScript modules</a></li></ol></details></li><li class="toggle"><details><summary>Intermediate</summary><ol><li><a href="/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects">Advanced JavaScript objects</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Async_JS">Asynchronous JavaScript</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Client-side_APIs">Client-side web APIs</a></li><li><a href="/en-US/docs/Web/JavaScript/Language_overview">Language overview</a></li><li><a href="/en-US/docs/Web/JavaScript/Data_structures">JavaScript data structures</a></li><li><a href="/en-US/docs/Web/JavaScript/Equality_comparisons_and_sameness">Equality comparisons and sameness</a></li><li><a href="/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_properties">Enumerability and ownership of properties</a></li><li><a href="/en-US/docs/Web/JavaScript/Closures">Closures</a></li></ol></details></li><li class="toggle"><details><summary>Advanced</summary><ol><li><a href="/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain">Inheritance and the prototype chain</a></li><li><a href="/en-US/docs/Web/JavaScript/Memory_management">Memory Management</a></li><li><a href="/en-US/docs/Web/JavaScript/Event_loop">Concurrency model and Event Loop</a></li></ol></details></li><li class="section"><a href="/en-US/docs/Web/JavaScript/Reference">References</a></li><li class="toggle"><details><summary>Built-in objects</summary><ol><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects">Overview</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/AggregateError">AggregateError</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array">Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer">ArrayBuffer</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction">AsyncFunction</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncGenerator">AsyncGenerator</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncGeneratorFunction">AsyncGeneratorFunction</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncIterator">AsyncIterator</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics">Atomics</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt">BigInt</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt64Array">BigInt64Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigUint64Array">BigUint64Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean">Boolean</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView">DataView</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date">Date</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/decodeURI">decodeURI()</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/decodeURIComponent">decodeURIComponent()</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURI">encodeURI()</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURIComponent">encodeURIComponent()</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error">Error</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/escape">escape()</a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval">eval()</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/EvalError">EvalError</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/FinalizationRegistry">FinalizationRegistry</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float16Array">Float16Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float32Array">Float32Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float64Array">Float64Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function">Function</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Generator">Generator</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/GeneratorFunction">GeneratorFunction</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/globalThis">globalThis</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity">Infinity</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int16Array">Int16Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int32Array">Int32Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int8Array">Int8Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/InternalError">InternalError</a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl">Intl</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/isFinite">isFinite()</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/isNaN">isNaN()</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Iterator">Iterator</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON">JSON</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map">Map</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math">Math</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/NaN">NaN</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number">Number</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object">Object</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseFloat">parseFloat()</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt">parseInt()</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise">Promise</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy">Proxy</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/RangeError">RangeError</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/ReferenceError">ReferenceError</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect">Reflect</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp">RegExp</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set">Set</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer">SharedArrayBuffer</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/String">String</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol">Symbol</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/SyntaxError">SyntaxError</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal">Temporal</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray">TypedArray</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError">TypeError</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint16Array">Uint16Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array">Uint32Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array">Uint8Array</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8ClampedArray">Uint8ClampedArray</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined">undefined</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/unescape">unescape()</a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/URIError">URIError</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap">WeakMap</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakRef">WeakRef</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet">WeakSet</a></li></ol></details></li><li class="toggle"><details><summary>Expressions & operators</summary><ol><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators">Overview</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Addition">Addition (+)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Addition_assignment">Addition assignment (+=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Assignment">Assignment (=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/async_function">async function expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/async_function*">async function* expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/await">await</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_AND">Bitwise AND (&)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_AND_assignment">Bitwise AND assignment (&=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_NOT">Bitwise NOT (~)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_OR">Bitwise OR (|)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_OR_assignment">Bitwise OR assignment (|=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_XOR">Bitwise XOR (^)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_XOR_assignment">Bitwise XOR assignment (^=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/class">class expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Comma_operator">Comma operator (,)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_operator">Conditional (ternary) operator</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Decrement">Decrement (--)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/delete">delete</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment">Destructuring assignment</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Division">Division (/)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Division_assignment">Division assignment (/=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Equality">Equality (==)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Exponentiation">Exponentiation (**)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Exponentiation_assignment">Exponentiation assignment (**=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/function">function expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/function*">function* expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Greater_than">Greater than (>)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Greater_than_or_equal">Greater than or equal (>=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Grouping">Grouping operator ( )</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/import.meta">import.meta</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/import">import()</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/in">in</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Increment">Increment (++)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Inequality">Inequality (!=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/instanceof">instanceof</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Left_shift">Left shift (<<)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Left_shift_assignment">Left shift assignment (<<=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Less_than">Less than (<)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Less_than_or_equal">Less than or equal (<=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Logical_AND">Logical AND (&&)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Logical_AND_assignment">Logical AND assignment (&&=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Logical_NOT">Logical NOT (!)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Logical_OR">Logical OR (||)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Logical_OR_assignment">Logical OR assignment (||=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Multiplication">Multiplication (*)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Multiplication_assignment">Multiplication assignment (*=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/new">new</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/new.target">new.target</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/null">null</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_assignment">Nullish coalescing assignment (??=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing">Nullish coalescing operator (??)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer">Object initializer</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Operator_precedence">Operator precedence</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining">Optional chaining (?.)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Property_accessors">Property accessors</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Remainder">Remainder (%)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Remainder_assignment">Remainder assignment (%=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Right_shift">Right shift (>>)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Right_shift_assignment">Right shift assignment (>>=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax">Spread syntax (...)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Strict_equality">Strict equality (===)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Strict_inequality">Strict inequality (!==)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Subtraction">Subtraction (-)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Subtraction_assignment">Subtraction assignment (-=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/super">super</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/this">this</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/typeof">typeof</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Unary_negation">Unary negation (-)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Unary_plus">Unary plus (+)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Unsigned_right_shift">Unsigned right shift (>>>)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Unsigned_right_shift_assignment">Unsigned right shift assignment (>>>=)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/void">void operator</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/yield">yield</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/yield*">yield*</a></li></ol></details></li><li class="toggle"><details open=""><summary>Statements & declarations</summary><ol><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements">Overview</a></li><li><em><a href="/en-US/docs/Web/JavaScript/Reference/Statements/async_function" aria-current="page">async function</a></em></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/async_function*">async function*</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/block">Block statement</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/break">break</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/class">class</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/const">const</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/continue">continue</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/debugger">debugger</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/do...while">do...while</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/Empty">Empty statement</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/export">export</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/Expression_statement">Expression statement</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/for">for</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/for-await...of">for await...of</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/for...in">for...in</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/for...of">for...of</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/function">function</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/function*">function*</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/if...else">if...else</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/import">import</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/label">Labeled statement</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/let">let</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/return">return</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/switch">switch</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/throw">throw</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/try...catch">try...catch</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/var">var</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/while">while</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/with">with</a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li></ol></details></li><li class="toggle"><details><summary>Functions</summary><ol><li><a href="/en-US/docs/Web/JavaScript/Reference/Functions">Overview</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions">Arrow function expressions</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters">Default parameters</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Functions/get">get</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Functions/Method_definitions">Method definitions</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters">Rest parameters</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Functions/set">set</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Functions/arguments">The arguments object</a></li></ol></details></li><li class="toggle"><details><summary>Classes</summary><ol><li><a href="/en-US/docs/Web/JavaScript/Reference/Classes">Overview</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Classes/constructor">constructor</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Classes/extends">extends</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Classes/Private_properties">Private properties</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Classes/Public_class_fields">Public class fields</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Classes/static">static</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Classes/Static_initialization_blocks">Static initialization blocks</a></li></ol></details></li><li class="toggle"><details><summary>Regular expressions</summary><ol><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions">Overview</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Backreference">Backreference: \1, \2</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Capturing_group">Capturing group: (...)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Character_class_escape">Character class escape: \d, \D, \w, \W, \s, \S</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Character_class">Character class: [...], [^...]</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Character_escape">Character escape: \n, \u{...}</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Disjunction">Disjunction: |</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Input_boundary_assertion">Input boundary assertion: ^, $</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Literal_character">Literal character: a, b</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Lookahead_assertion">Lookahead assertion: (?=...), (?!...)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Lookbehind_assertion">Lookbehind assertion: (?<=...), (?<!...)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Modifier">Modifier: (?ims-ims:...)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Named_backreference">Named backreference: \k<name></a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Named_capturing_group">Named capturing group: (?<name>...)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Non-capturing_group">Non-capturing group: (?:...)</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Quantifier">Quantifier: *, +, ?, {n}, {n,}, {n,m}</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Unicode_character_class_escape">Unicode character class escape: \p{...}, \P{...}</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Wildcard">Wildcard: .</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Word_boundary_assertion">Word boundary assertion: \b, \B</a></li></ol></details></li><li class="toggle"><details><summary>Errors</summary><ol><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors">Overview</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Promise_any_all_rejected">AggregateError: No Promise in Promise.any was resolved</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Property_access_denied">Error: Permission denied to access property "x"</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Too_much_recursion">InternalError: too much recursion</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Not_a_valid_code_point">RangeError: argument is not a valid code point</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/BigInt_division_by_zero">RangeError: BigInt division by zero</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/BigInt_negative_exponent">RangeError: BigInt negative exponent</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Form_must_be_one_of">RangeError: form must be one of 'NFC', 'NFD', 'NFKC', or 'NFKD'</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_array_length">RangeError: invalid array length</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_date">RangeError: invalid date</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Precision_range">RangeError: precision is out of range</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_radix">RangeError: radix must be an integer</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Resulting_string_too_large">RangeError: repeat count must be less than infinity</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Negative_repetition_count">RangeError: repeat count must be non-negative</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_be_converted_to_BigInt_because_it_isnt_an_integer">RangeError: x can't be converted to BigInt because it isn't an integer</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Not_defined">ReferenceError: "x" is not defined</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Undeclared_var">ReferenceError: assignment to undeclared variable "x"</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_access_lexical_declaration_before_init">ReferenceError: can't access lexical declaration 'X' before initialization</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Deprecated_caller_or_arguments_usage">ReferenceError: deprecated caller or arguments usage</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Super_not_called">ReferenceError: must call super constructor before using 'this' in derived class constructor</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Super_called_twice">ReferenceError: super() called twice in derived class constructor</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_strict_arguments_eval">SyntaxError: 'arguments'/'eval' can't be defined or assigned to in strict mode code</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Deprecated_octal_literal">SyntaxError: "0"-prefixed octal literals are deprecated</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Strict_non_simple_params">SyntaxError: "use strict" not allowed in function with non-simple parameters</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Reserved_identifier">SyntaxError: "x" is a reserved identifier</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_backslash_at_end_of_pattern">SyntaxError: \ at end of pattern</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_for-of_initializer">SyntaxError: a declaration in the head of a for-of loop can't have an initializer</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Delete_in_strict_mode">SyntaxError: applying the 'delete' operator to an unqualified name is deprecated</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Arguments_not_allowed">SyntaxError: arguments is not valid in fields</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_await">SyntaxError: await is only valid in async functions, async generators and modules</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/await_yield_in_parameter">SyntaxError: await/yield expression can't be used in parameter</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_use_nullish_coalescing_unparenthesized">SyntaxError: cannot use `??` unparenthesized within `||` and `&&` expressions</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_character_class_escape_in_class_range">SyntaxError: character class escape cannot be used in class range in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_continue">SyntaxError: continue must be inside loop</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_duplicate_capture_group_name">SyntaxError: duplicate capture group name in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Duplicate_parameter">SyntaxError: duplicate formal argument x</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_for-in_initializer">SyntaxError: for-in loop head declarations may not have initializers</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Unnamed_function_statement">SyntaxError: function statement requires a name</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Function_label">SyntaxError: functions cannot be labelled</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Either_be_both_static_or_non-static">SyntaxError: getter and setter for private name #x should either be both static or non-static</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Getter_no_arguments">SyntaxError: getter functions must have no arguments</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Identifier_after_number">SyntaxError: identifier starts immediately after numeric literal</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Illegal_character">SyntaxError: illegal character</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/import_decl_module_top_level">SyntaxError: import declarations may only appear at top level of a module</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_incomplete_quantifier">SyntaxError: incomplete quantifier in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_assignment_left-hand_side">SyntaxError: invalid assignment left-hand side</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_BigInt_syntax">SyntaxError: invalid BigInt syntax</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_capture_group_name">SyntaxError: invalid capture group name in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_char_in_class">SyntaxError: invalid character in class in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_class_set_operation">SyntaxError: invalid class set operation in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_decimal_escape">SyntaxError: invalid decimal escape in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_identity_escape">SyntaxError: invalid identity escape in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_named_capture_reference">SyntaxError: invalid named capture reference in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_property_name">SyntaxError: invalid property name in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_range_in_character_class">SyntaxError: invalid range in character class</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_group">SyntaxError: invalid regexp group</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_regexp_flag">SyntaxError: invalid regular expression flag "x"</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_unicode_escape">SyntaxError: invalid unicode escape in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/JSON_bad_parse">SyntaxError: JSON.parse: bad parsing</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Label_not_found">SyntaxError: label not found</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Missing_colon_after_property_id">SyntaxError: missing : after property id</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Missing_parenthesis_after_argument_list">SyntaxError: missing ) after argument list</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Missing_parenthesis_after_condition">SyntaxError: missing ) after condition</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Missing_bracket_after_list">SyntaxError: missing ] after element list</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Missing_curly_after_function_body">SyntaxError: missing } after function body</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Missing_curly_after_property_list">SyntaxError: missing } after property list</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Missing_initializer_in_const">SyntaxError: missing = in const declaration</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Missing_formal_parameter">SyntaxError: missing formal parameter</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Missing_name_after_dot_operator">SyntaxError: missing name after . operator</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/No_variable_name">SyntaxError: missing variable name</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_negated_char_class_with_strings">SyntaxError: negated character class with strings in regular expression</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_new_optional">SyntaxError: new keyword cannot be used with an optional chain</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_nothing_to_repeat">SyntaxError: nothing to repeat</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_numbers_out_of_order_in_quantifier">SyntaxError: numbers out of order in {} quantifier.</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Deprecated_octal_escape_sequence">SyntaxError: octal escape sequences can't be used in untagged template literals or in strict mode code</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Parameter_after_rest_parameter">SyntaxError: parameter after rest parameter</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_delete_private_fields">SyntaxError: private fields can't be deleted</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Duplicate_proto">SyntaxError: property name __proto__ appears more than once in object literal</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Regex_raw_bracket">SyntaxError: raw bracket is not allowed in regular expression with unicode flag</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Redeclared_parameter">SyntaxError: redeclaration of formal parameter "x"</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Undeclared_private_field_or_method">SyntaxError: reference to undeclared private field or method #x</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Rest_with_default">SyntaxError: rest parameter may not have a default</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_return">SyntaxError: return not in function</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Setter_one_argument">SyntaxError: setter functions must have one argument</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/String_literal_EOL">SyntaxError: string literal contains an unescaped line break</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_super_call">SyntaxError: super() is only valid in derived class constructors</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_optional_template">SyntaxError: tagged template cannot be used with optional chain</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Hash_outside_class">SyntaxError: Unexpected '#' used outside of class body</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Unexpected_token">SyntaxError: Unexpected token</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_break">SyntaxError: unlabeled break must be inside loop or switch</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Unparenthesized_unary_expr_lhs_exponentiation">SyntaxError: unparenthesized unary expression can't appear on the left-hand side of '**'</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Bad_super_prop">SyntaxError: use of super property/member accesses only valid within methods or eval code within methods</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Deprecated_source_map_pragma">SyntaxError: Using //@ to indicate sourceURL pragmas is deprecated. Use //# instead</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/is_not_iterable">TypeError: 'x' is not iterable</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Unexpected_type">TypeError: "x" is (not) "y"</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Not_a_constructor">TypeError: "x" is not a constructor</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Not_a_function">TypeError: "x" is not a function</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/No_non-null_object">TypeError: "x" is not a non-null object</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Read-only">TypeError: "x" is read-only</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/BigInt_not_serializable">TypeError: BigInt value can't be serialized in JSON</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Builtin_ctor_no_new">TypeError: calling a builtin X constructor without new is forbidden</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Get_set_missing_private">TypeError: can't access/set private field or method: object is not the right class</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_assign_to_property">TypeError: can't assign to property "x" on "y": not an object</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_convert_BigInt_to_number">TypeError: can't convert BigInt to number</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_convert_x_to_BigInt">TypeError: can't convert x to BigInt</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_define_property_object_not_extensible">TypeError: can't define property "x": "obj" is not extensible</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Non_configurable_array_element">TypeError: can't delete non-configurable array element</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_redefine_property">TypeError: can't redefine non-configurable property "x"</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_set_prototype">TypeError: can't set prototype of this object</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cyclic_prototype">TypeError: can't set prototype: it would cause a prototype chain cycle</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/in_operator_no_object">TypeError: cannot use 'in' operator to search for 'x' in 'y'</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Class_ctor_no_new">TypeError: class constructors must be invoked with 'new'</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cyclic_object_value">TypeError: cyclic object value</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_derived_return">TypeError: derived class constructor returned invalid value x</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Private_setter_only">TypeError: getting private setter-only property</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Private_double_initialization">TypeError: Initializing an object twice is an error with private fields/methods</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/invalid_right_hand_side_instanceof_operand">TypeError: invalid 'instanceof' operand 'x'</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Array_sort_argument">TypeError: invalid Array.prototype.sort argument</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_const_assignment">TypeError: invalid assignment to const "x"</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Constructor_cant_be_used_directly">TypeError: Iterator/AsyncIterator constructor can't be used directly</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Requires_global_RegExp">TypeError: matchAll/replaceAll must be called with a global RegExp</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/More_arguments_needed">TypeError: More arguments needed</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/No_properties">TypeError: null/undefined has no properties</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_delete">TypeError: property "x" is non-configurable and can't be deleted</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Reduce_of_empty_array_with_no_initial_value">TypeError: Reduce of empty array with no initial value</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Getter_only">TypeError: setting getter-only property "x"</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Key_not_weakly_held">TypeError: WeakSet key/WeakMap value 'x' must be an object or an unregistered symbol</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Called_on_incompatible_type">TypeError: X.prototype.y called on incompatible type</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Malformed_URI">URIError: malformed URI sequence</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Already_has_pragma">Warning: -file- is being assigned a //# sourceMappingURL, but already has one</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Stmt_after_return">Warning: unreachable code after return statement</a></li></ol></details></li><li class="toggle"><details><summary>Misc</summary><ol><li><a href="/en-US/docs/Web/JavaScript/JavaScript_technologies_overview">JavaScript technologies overview</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Lexical_grammar">Lexical grammar</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">Iteration protocols</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Strict_mode">Strict mode</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Template_literals">Template literals</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Trailing_commas">Trailing commas</a></li><li><a href="/en-US/docs/Web/JavaScript/Reference/Deprecated_and_obsolete_features">Deprecated features</a></li></ol></details></li></ol></div></div><section class="place side"></section></nav></aside><div class="toc-container"><aside class="toc"><nav><div class="document-toc-container"><section class="document-toc"><header><h2 class="document-toc-heading">In this article</h2></header><ul class="document-toc-list"><li class="document-toc-item "><a class="document-toc-link" href="#try_it">Try it</a></li><li class="document-toc-item "><a class="document-toc-link" href="#syntax">Syntax</a></li><li class="document-toc-item "><a class="document-toc-link" href="#description">Description</a></li><li class="document-toc-item "><a class="document-toc-link" href="#examples">Examples</a></li><li class="document-toc-item "><a class="document-toc-link" href="#specifications">Specifications</a></li><li class="document-toc-item "><a class="document-toc-link" href="#browser_compatibility">Browser compatibility</a></li><li class="document-toc-item "><a class="document-toc-link" href="#see_also">See also</a></li></ul></section></div></nav></aside><section class="place side"></section></div></div><main id="content" class="main-content "><article class="main-page-content" lang="en-US"><header><h1>async function</h1><details class="baseline-indicator high"><summary><span class="indicator" role="img" aria-label="Baseline Check"></span><div class="status-title">Baseline <span class="not-bold">Widely available</span></div><div class="browsers"><span class="engine" title="Supported in Chrome and Edge"><span class="browser chrome supported" role="img" aria-label="Chrome check"></span><span class="browser edge supported" role="img" aria-label="Edge check"></span></span><span class="engine" title="Supported in Firefox"><span class="browser firefox supported" role="img" aria-label="Firefox check"></span></span><span class="engine" title="Supported in Safari"><span class="browser safari supported" role="img" aria-label="Safari check"></span></span></div><span class="icon icon-chevron "></span></summary><div class="extra"><p>This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2017.</p><ul><li><a href="/en-US/docs/Glossary/Baseline/Compatibility" data-glean="baseline_link_learn_more" target="_blank" class="learn-more">Learn more</a></li><li><a href="#browser_compatibility" data-glean="baseline_link_bcd_table">See full compatibility</a></li><li><a href="https://survey.alchemer.com/s3/7634825/MDN-baseline-feedback?page=%2Fen-US%2Fdocs%2FWeb%2FJavaScript%2FReference%2FStatements%2Fasync_function&level=high" data-glean="baseline_link_feedback" class="feedback-link" target="_blank" rel="noreferrer">Report feedback</a></li></ul></div></details></header><div class="section-content"><p>The <strong><code>async function</code></strong> declaration creates a <a href="/en-US/docs/Glossary/Binding">binding</a> of a new async function to a given name. The <code>await</code> keyword is permitted within the function body, enabling asynchronous, promise-based behavior to be written in a cleaner style and avoiding the need to explicitly configure promise chains.</p> <p>You can also define async functions using the <a href="/en-US/docs/Web/JavaScript/Reference/Operators/async_function"><code>async function</code> expression</a>.</p></div><section aria-labelledby="try_it"><h2 id="try_it"><a href="#try_it">Try it</a></h2><div class="section-content"><interactive-example name="JavaScript Demo: Statement - Async" height="taller"></interactive-example> <div class="code-example"><pre class="brush: js interactive-example notranslate"><code>function resolveAfter2Seconds() { return new Promise((resolve) => { setTimeout(() => { resolve("resolved"); }, 2000); }); } async function asyncCall() { console.log("calling"); const result = await resolveAfter2Seconds(); console.log(result); // Expected output: "resolved" } asyncCall(); </code></pre></div></div></section><section aria-labelledby="syntax"><h2 id="syntax"><a href="#syntax">Syntax</a></h2><div class="section-content"><div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>async function name(param0) { statements } async function name(param0, param1) { statements } async function name(param0, param1, /* …, */ paramN) { statements } </code></pre></div> <div class="notecard note"> <p><strong>Note:</strong> There cannot be a line terminator between <code>async</code> and <code>function</code>, otherwise a semicolon is <a href="/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#automatic_semicolon_insertion">automatically inserted</a>, causing <code>async</code> to become an identifier and the rest to become a <code>function</code> declaration.</p> </div></div></section><section aria-labelledby="parameters"><h3 id="parameters"><a href="#parameters">Parameters</a></h3><div class="section-content"><dl> <dt id="name"><a href="#name"><code>name</code></a></dt> <dd> <p>The function's name.</p> </dd> <dt id="param"><a href="#param"><code>param</code> <span class="badge inline optional">Optional</span></a></dt> <dd> <p>The name of a formal parameter for the function. For the parameters' syntax, see the <a href="/en-US/docs/Web/JavaScript/Guide/Functions#function_parameters">Functions reference</a>.</p> </dd> <dt id="statements"><a href="#statements"><code>statements</code> <span class="badge inline optional">Optional</span></a></dt> <dd> <p>The statements comprising the body of the function. The <code>await</code> mechanism may be used.</p> </dd> </dl></div></section><section aria-labelledby="description"><h2 id="description"><a href="#description">Description</a></h2><div class="section-content"><p>An <code>async function</code> declaration creates an <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction"><code>AsyncFunction</code></a> object. Each time when an async function is called, it returns a new <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise"><code>Promise</code></a> which will be resolved with the value returned by the async function, or rejected with an exception uncaught within the async function.</p> <p>Async functions can contain zero or more <a href="/en-US/docs/Web/JavaScript/Reference/Operators/await"><code>await</code></a> expressions. Await expressions make promise-returning functions behave as though they're synchronous by suspending execution until the returned promise is fulfilled or rejected. The resolved value of the promise is treated as the return value of the await expression. Use of <code>async</code> and <code>await</code> enables the use of ordinary <code>try</code> / <code>catch</code> blocks around asynchronous code.</p> <div class="notecard note"> <p><strong>Note:</strong> The <code>await</code> keyword is only valid inside async functions within regular JavaScript code. If you use it outside of an async function's body, you will get a <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/SyntaxError"><code>SyntaxError</code></a>.</p> <p><code>await</code> can be used on its own with <a href="/en-US/docs/Web/JavaScript/Guide/Modules">JavaScript modules.</a></p> </div> <div class="notecard note"> <p><strong>Note:</strong> The purpose of <code>async</code>/<code>await</code> is to simplify the syntax necessary to consume promise-based APIs. The behavior of <code>async</code>/<code>await</code> is similar to combining <a href="/en-US/docs/Web/JavaScript/Guide/Iterators_and_generators">generators</a> and promises.</p> </div> <p>Async functions always return a promise. If the return value of an async function is not explicitly a promise, it will be implicitly wrapped in a promise.</p> <p>For example, consider the following code:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>async function foo() { return 1; } </code></pre></div> <p>It is similar to:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function foo() { return Promise.resolve(1); } </code></pre></div> <p>Note that even though the return value of an async function behaves as if it's wrapped in a <code>Promise.resolve</code>, they are not equivalent. An async function will return a different <em>reference</em>, whereas <code>Promise.resolve</code> returns the same reference if the given value is a promise. It can be a problem when you want to check the equality of a promise and a return value of an async function.</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>const p = new Promise((res, rej) => { res(1); }); async function asyncReturn() { return p; } function basicReturn() { return Promise.resolve(p); } console.log(p === basicReturn()); // true console.log(p === asyncReturn()); // false </code></pre></div> <p>The body of an async function can be thought of as being split by zero or more await expressions. Top-level code, up to and including the first await expression (if there is one), is run synchronously. In this way, an async function without an await expression will run synchronously. If there is an await expression inside the function body, however, the async function will always complete asynchronously.</p> <p>For example:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>async function foo() { await 1; } </code></pre></div> <p>It is also equivalent to:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function foo() { return Promise.resolve(1).then(() => undefined); } </code></pre></div> <p>Code after each await expression can be thought of as existing in a <code>.then</code> callback. In this way a promise chain is progressively constructed with each reentrant step through the function. The return value forms the final link in the chain.</p> <p>In the following example, we successively await two promises. Progress moves through function <code>foo</code> in three stages.</p> <ol> <li>The first line of the body of function <code>foo</code> is executed synchronously, with the await expression configured with the pending promise. Progress through <code>foo</code> is then suspended and control is yielded back to the function that called <code>foo</code>.</li> <li>Some time later, when the first promise has either been fulfilled or rejected, control moves back into <code>foo</code>. The result of the first promise fulfillment (if it was not rejected) is returned from the await expression. Here <code>1</code> is assigned to <code>result1</code>. Progress continues, and the second await expression is evaluated. Again, progress through <code>foo</code> is suspended and control is yielded.</li> <li>Some time later, when the second promise has either been fulfilled or rejected, control re-enters <code>foo</code>. The result of the second promise resolution is returned from the second await expression. Here <code>2</code> is assigned to <code>result2</code>. Control moves to the return expression (if any). The default return value of <code>undefined</code> is returned as the resolution value of the current promise.</li> </ol> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>async function foo() { const result1 = await new Promise((resolve) => setTimeout(() => resolve("1")), ); const result2 = await new Promise((resolve) => setTimeout(() => resolve("2")), ); } foo(); </code></pre></div> <p>Note how the promise chain is not built-up in one go. Instead, the promise chain is constructed in stages as control is successively yielded from and returned to the async function. As a result, we must be mindful of error handling behavior when dealing with concurrent asynchronous operations.</p> <p>For example, in the following code an unhandled promise rejection error will be thrown, even if a <code>.catch</code> handler has been configured further along the promise chain. This is because <code>p2</code> will not be "wired into" the promise chain until control returns from <code>p1</code>.</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>async function foo() { const p1 = new Promise((resolve) => setTimeout(() => resolve("1"), 1000)); const p2 = new Promise((_, reject) => setTimeout(() => reject("2"), 500)); const results = [await p1, await p2]; // Do not do this! Use Promise.all or Promise.allSettled instead. } foo().catch(() => {}); // Attempt to swallow all errors... </code></pre></div> <p><code>async function</code> declarations behave similar to <a href="/en-US/docs/Web/JavaScript/Reference/Statements/function"><code>function</code></a> declarations — they are <a href="/en-US/docs/Glossary/Hoisting">hoisted</a> to the top of their scope and can be called anywhere in their scope, and they can be redeclared only in certain contexts.</p></div></section><section aria-labelledby="examples"><h2 id="examples"><a href="#examples">Examples</a></h2><div class="section-content"></div></section><section aria-labelledby="async_functions_and_execution_order"><h3 id="async_functions_and_execution_order"><a href="#async_functions_and_execution_order">Async functions and execution order</a></h3><div class="section-content"><div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function resolveAfter2Seconds() { console.log("starting slow promise"); return new Promise((resolve) => { setTimeout(() => { resolve("slow"); console.log("slow promise is done"); }, 2000); }); } function resolveAfter1Second() { console.log("starting fast promise"); return new Promise((resolve) => { setTimeout(() => { resolve("fast"); console.log("fast promise is done"); }, 1000); }); } async function sequentialStart() { console.log("== sequentialStart starts =="); // 1. Start a timer, log after it's done const slow = resolveAfter2Seconds(); console.log(await slow); // 2. Start the next timer after waiting for the previous one const fast = resolveAfter1Second(); console.log(await fast); console.log("== sequentialStart done =="); } async function sequentialWait() { console.log("== sequentialWait starts =="); // 1. Start two timers without waiting for each other const slow = resolveAfter2Seconds(); const fast = resolveAfter1Second(); // 2. Wait for the slow timer to complete, and then log the result console.log(await slow); // 3. Wait for the fast timer to complete, and then log the result console.log(await fast); console.log("== sequentialWait done =="); } async function concurrent1() { console.log("== concurrent1 starts =="); // 1. Start two timers concurrently and wait for both to complete const results = await Promise.all([ resolveAfter2Seconds(), resolveAfter1Second(), ]); // 2. Log the results together console.log(results[0]); console.log(results[1]); console.log("== concurrent1 done =="); } async function concurrent2() { console.log("== concurrent2 starts =="); // 1. Start two timers concurrently, log immediately after each one is done await Promise.all([ (async () => console.log(await resolveAfter2Seconds()))(), (async () => console.log(await resolveAfter1Second()))(), ]); console.log("== concurrent2 done =="); } sequentialStart(); // after 2 seconds, logs "slow", then after 1 more second, "fast" // wait above to finish setTimeout(sequentialWait, 4000); // after 2 seconds, logs "slow" and then "fast" // wait again setTimeout(concurrent1, 7000); // same as sequentialWait // wait again setTimeout(concurrent2, 10000); // after 1 second, logs "fast", then after 1 more second, "slow" </code></pre></div> <h4 id="await_and_concurrency">await and concurrency</h4> <p>In <code>sequentialStart</code>, execution suspends 2 seconds for the first <code>await</code>, and then another second for the second <code>await</code>. The second timer is not created until the first has already fired, so the code finishes after 3 seconds.</p> <p>In <code>sequentialWait</code>, both timers are created and then <code>await</code>ed. The timers run concurrently, which means the code finishes in 2 rather than 3 seconds, i.e. the slowest timer. However, the <code>await</code> calls still run in series, which means the second <code>await</code> will wait for the first one to finish. In this case, the result of the fastest timer is processed after the slowest.</p> <p>If you wish to safely perform other jobs after two or more jobs run concurrently and are complete, you must await a call to <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all"><code>Promise.all()</code></a> or <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/allSettled"><code>Promise.allSettled()</code></a> before that job.</p> <div class="notecard warning"> <p><strong>Warning:</strong> The functions <code>sequentialWait</code> and <code>concurrent1</code> are not functionally equivalent.</p> <p>In <code>sequentialWait</code>, if promise <code>fast</code> rejects before promise <code>slow</code> is fulfilled, then an unhandled promise rejection error will be raised, regardless of whether the caller has configured a catch clause.</p> <p>In <code>concurrent1</code>, <code>Promise.all</code> wires up the promise chain in one go, meaning that the operation will fail-fast regardless of the order of rejection of the promises, and the error will always occur within the configured promise chain, enabling it to be caught in the normal way.</p> </div></div></section><section aria-labelledby="rewriting_a_promise_chain_with_an_async_function"><h3 id="rewriting_a_promise_chain_with_an_async_function"><a href="#rewriting_a_promise_chain_with_an_async_function">Rewriting a Promise chain with an async function</a></h3><div class="section-content"><p>An API that returns a <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise"><code>Promise</code></a> will result in a promise chain, and it splits the function into many parts. Consider the following code:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function getProcessedData(url) { return downloadData(url) // returns a promise .catch((e) => downloadFallbackData(url)) // returns a promise .then((v) => processDataInWorker(v)); // returns a promise } </code></pre></div> <p>it can be rewritten with a single async function as follows:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>async function getProcessedData(url) { let v; try { v = await downloadData(url); } catch (e) { v = await downloadFallbackData(url); } return processDataInWorker(v); } </code></pre></div> <p>Alternatively, you can chain the promise with <code>catch()</code>:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>async function getProcessedData(url) { const v = await downloadData(url).catch((e) => downloadFallbackData(url)); return processDataInWorker(v); } </code></pre></div> <p>In the two rewritten versions, notice there is no <code>await</code> statement after the <code>return</code> keyword, although that would be valid too: The return value of an async function is implicitly wrapped in <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/resolve"><code>Promise.resolve</code></a> - if it's not already a promise itself (as in the examples).</p></div></section><h2 id="specifications"><a href="#specifications">Specifications</a></h2><table class="standard-table"><thead><tr><th scope="col">Specification</th></tr></thead><tbody><tr><td><a href="https://tc39.es/ecma262/multipage/ecmascript-language-functions-and-classes.html#sec-async-function-definitions">ECMAScript® 2025 Language Specification <br/><small># sec-async-function-definitions</small></a></td></tr></tbody></table><h2 id="browser_compatibility"><a href="#browser_compatibility">Browser compatibility</a></h2><p>BCD tables only load in the browser<noscript> with JavaScript enabled. Enable JavaScript to view data.</noscript></p><section aria-labelledby="see_also"><h2 id="see_also"><a href="#see_also">See also</a></h2><div class="section-content"><ul> <li><a href="/en-US/docs/Web/JavaScript/Guide/Functions">Functions</a> guide</li> <li><a href="/en-US/docs/Web/JavaScript/Guide/Using_promises">Using promises</a> guide</li> <li><a href="/en-US/docs/Web/JavaScript/Reference/Functions">Functions</a></li> <li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction"><code>AsyncFunction</code></a></li> <li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/async_function"><code>async function</code> expression</a></li> <li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/function"><code>function</code></a></li> <li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/function*"><code>function*</code></a></li> <li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/async_function*"><code>async function*</code></a></li> <li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/await"><code>await</code></a></li> <li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise"><code>Promise</code></a></li> <li><a href="https://innolitics.com/10x/javascript-decorators-for-promise-returning-functions/" class="external" target="_blank">Decorating async JavaScript functions</a> on innolitics.com (2016)</li> </ul></div></section></article><aside class="article-footer"><div class="article-footer-inner"><div class="svg-container"><svg xmlns="http://www.w3.org/2000/svg" width="162" height="162" viewBox="0 0 162 162" fill="none" role="none"><mask id="b" fill="#fff"><path d="M97.203 47.04c8.113-7.886 18.004-13.871 28.906-17.492a78 78 0 0 1 33.969-3.39c11.443 1.39 22.401 5.295 32.024 11.411s17.656 14.28 23.476 23.86c5.819 9.579 9.269 20.318 10.083 31.385a69.85 69.85 0 0 1-5.387 32.44c-4.358 10.272-11.115 19.443-19.747 26.801-8.632 7.359-18.908 12.709-30.034 15.637l-6.17-21.698c7.666-2.017 14.746-5.703 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contributors. Content available under <a href="/en-US/docs/MDN/Writing_guidelines/Attrib_copyright_license">a Creative Commons license</a>.</p></div></div></footer></div><script type="application/json" id="hydration">{"url":"/en-US/docs/Web/JavaScript/Reference/Statements/async_function","doc":{"body":[{"type":"prose","value":{"id":null,"title":null,"isH3":false,"content":"<p>The <strong><code>async function</code></strong> declaration creates a <a href=\"/en-US/docs/Glossary/Binding\">binding</a> of a new async function to a given name. The <code>await</code> keyword is permitted within the function body, enabling asynchronous, promise-based behavior to be written in a cleaner style and avoiding the need to explicitly configure promise chains.</p>\n<p>You can also define async functions using the <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/async_function\"><code>async function</code> expression</a>.</p>"}},{"type":"prose","value":{"id":"try_it","title":"Try it","isH3":false,"content":"<interactive-example name=\"JavaScript Demo: Statement - Async\" height=\"taller\"></interactive-example>\n<div class=\"code-example\"><pre class=\"brush: js interactive-example notranslate\"><code>function resolveAfter2Seconds() {\n return new Promise((resolve) => {\n setTimeout(() => {\n resolve(\"resolved\");\n }, 2000);\n });\n}\n\nasync function asyncCall() {\n console.log(\"calling\");\n const result = await resolveAfter2Seconds();\n console.log(result);\n // Expected output: \"resolved\"\n}\n\nasyncCall();\n</code></pre></div>"}},{"type":"prose","value":{"id":"syntax","title":"Syntax","isH3":false,"content":"<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>async function name(param0) {\n statements\n}\nasync function name(param0, param1) {\n statements\n}\nasync function name(param0, param1, /* …, */ paramN) {\n statements\n}\n</code></pre></div>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nThere cannot be a line terminator between <code>async</code> and <code>function</code>, otherwise a semicolon is <a href=\"/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#automatic_semicolon_insertion\">automatically inserted</a>, causing <code>async</code> to become an identifier and the rest to become a <code>function</code> declaration.</p>\n</div>"}},{"type":"prose","value":{"id":"parameters","title":"Parameters","isH3":true,"content":"<dl>\n<dt id=\"name\"><a href=\"#name\"><code>name</code></a></dt>\n<dd>\n<p>The function's name.</p>\n</dd>\n<dt id=\"param\"><a href=\"#param\"><code>param</code> <span class=\"badge inline optional\">Optional</span></a></dt>\n<dd>\n<p>The name of a formal parameter for the function. For the parameters' syntax, see the <a href=\"/en-US/docs/Web/JavaScript/Guide/Functions#function_parameters\">Functions reference</a>.</p>\n</dd>\n<dt id=\"statements\"><a href=\"#statements\"><code>statements</code> <span class=\"badge inline optional\">Optional</span></a></dt>\n<dd>\n<p>The statements comprising the body of the function. The <code>await</code>\nmechanism may be used.</p>\n</dd>\n</dl>"}},{"type":"prose","value":{"id":"description","title":"Description","isH3":false,"content":"<p>An <code>async function</code> declaration creates an <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction\"><code>AsyncFunction</code></a> object. Each time when an async function is called, it returns a new <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise\"><code>Promise</code></a> which will be resolved with the value returned by the async function, or rejected with an exception uncaught within the async function.</p>\n<p>Async functions can contain zero or more <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/await\"><code>await</code></a> expressions. Await expressions make promise-returning functions behave as though they're synchronous by suspending execution until the returned promise is fulfilled or rejected. The resolved value of the promise is treated as the return value of the await expression. Use of <code>async</code> and <code>await</code> enables the use of ordinary <code>try</code> / <code>catch</code> blocks around asynchronous code.</p>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nThe <code>await</code> keyword is only valid inside async functions within regular JavaScript code. If you use it outside of an async function's body, you will get a <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SyntaxError\"><code>SyntaxError</code></a>.</p>\n<p><code>await</code> can be used on its own with <a href=\"/en-US/docs/Web/JavaScript/Guide/Modules\">JavaScript modules.</a></p>\n</div>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nThe purpose of <code>async</code>/<code>await</code> is to simplify the syntax\nnecessary to consume promise-based APIs. The behavior\nof <code>async</code>/<code>await</code> is similar to combining <a href=\"/en-US/docs/Web/JavaScript/Guide/Iterators_and_generators\">generators</a> and\npromises.</p>\n</div>\n<p>Async functions always return a promise. If the return value of an async function is\nnot explicitly a promise, it will be implicitly wrapped in a promise.</p>\n<p>For example, consider the following code:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>async function foo() {\n return 1;\n}\n</code></pre></div>\n<p>It is similar to:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function foo() {\n return Promise.resolve(1);\n}\n</code></pre></div>\n<p>Note that even though the return value of an async function behaves as if it's wrapped in a <code>Promise.resolve</code>, they are not equivalent. An async function will return a different <em>reference</em>, whereas <code>Promise.resolve</code> returns the same reference if the given value is a promise. It can be a problem when you want to check the equality of a promise and a return value of an async function.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const p = new Promise((res, rej) => {\n res(1);\n});\n\nasync function asyncReturn() {\n return p;\n}\n\nfunction basicReturn() {\n return Promise.resolve(p);\n}\n\nconsole.log(p === basicReturn()); // true\nconsole.log(p === asyncReturn()); // false\n</code></pre></div>\n<p>The body of an async function can be thought of as being split by zero or more await\nexpressions. Top-level code, up to and including the first await expression (if there is\none), is run synchronously. In this way, an async function without an await expression\nwill run synchronously. If there is an await expression inside the function body,\nhowever, the async function will always complete asynchronously.</p>\n<p>For example:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>async function foo() {\n await 1;\n}\n</code></pre></div>\n<p>It is also equivalent to:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function foo() {\n return Promise.resolve(1).then(() => undefined);\n}\n</code></pre></div>\n<p>Code after each await expression can be thought of as existing in a <code>.then</code>\ncallback. In this way a promise chain is progressively constructed with each reentrant\nstep through the function. The return value forms the final link in the chain.</p>\n<p>In the following example, we successively await two promises. Progress moves through\nfunction <code>foo</code> in three stages.</p>\n<ol>\n<li>The first line of the body of function <code>foo</code> is executed synchronously,\nwith the await expression configured with the pending promise. Progress through\n<code>foo</code> is then suspended and control is yielded back to the function that\ncalled <code>foo</code>.</li>\n<li>Some time later, when the first promise has either been fulfilled or rejected,\ncontrol moves back into <code>foo</code>. The result of the first promise fulfillment\n(if it was not rejected) is returned from the await expression. Here <code>1</code> is\nassigned to <code>result1</code>. Progress continues, and the second await expression\nis evaluated. Again, progress through <code>foo</code> is suspended and control is\nyielded.</li>\n<li>Some time later, when the second promise has either been fulfilled or rejected,\ncontrol re-enters <code>foo</code>. The result of the second promise resolution is\nreturned from the second await expression. Here <code>2</code> is assigned to\n<code>result2</code>. Control moves to the return expression (if any). The default\nreturn value of <code>undefined</code> is returned as the resolution value of the\ncurrent promise.</li>\n</ol>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>async function foo() {\n const result1 = await new Promise((resolve) =>\n setTimeout(() => resolve(\"1\")),\n );\n const result2 = await new Promise((resolve) =>\n setTimeout(() => resolve(\"2\")),\n );\n}\nfoo();\n</code></pre></div>\n<p>Note how the promise chain is not built-up in one go. Instead, the promise chain is\nconstructed in stages as control is successively yielded from and returned to the async\nfunction. As a result, we must be mindful of error handling behavior when dealing with\nconcurrent asynchronous operations.</p>\n<p>For example, in the following code an unhandled promise rejection error will be thrown,\neven if a <code>.catch</code> handler has been configured further along the promise\nchain. This is because <code>p2</code> will not be \"wired into\" the promise chain until\ncontrol returns from <code>p1</code>.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>async function foo() {\n const p1 = new Promise((resolve) => setTimeout(() => resolve(\"1\"), 1000));\n const p2 = new Promise((_, reject) => setTimeout(() => reject(\"2\"), 500));\n const results = [await p1, await p2]; // Do not do this! Use Promise.all or Promise.allSettled instead.\n}\nfoo().catch(() => {}); // Attempt to swallow all errors...\n</code></pre></div>\n<p><code>async function</code> declarations behave similar to <a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/function\"><code>function</code></a> declarations — they are <a href=\"/en-US/docs/Glossary/Hoisting\">hoisted</a> to the top of their scope and can be called anywhere in their scope, and they can be redeclared only in certain contexts.</p>"}},{"type":"prose","value":{"id":"examples","title":"Examples","isH3":false,"content":""}},{"type":"prose","value":{"id":"async_functions_and_execution_order","title":"Async functions and execution order","isH3":true,"content":"<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function resolveAfter2Seconds() {\n console.log(\"starting slow promise\");\n return new Promise((resolve) => {\n setTimeout(() => {\n resolve(\"slow\");\n console.log(\"slow promise is done\");\n }, 2000);\n });\n}\n\nfunction resolveAfter1Second() {\n console.log(\"starting fast promise\");\n return new Promise((resolve) => {\n setTimeout(() => {\n resolve(\"fast\");\n console.log(\"fast promise is done\");\n }, 1000);\n });\n}\n\nasync function sequentialStart() {\n console.log(\"== sequentialStart starts ==\");\n\n // 1. Start a timer, log after it's done\n const slow = resolveAfter2Seconds();\n console.log(await slow);\n\n // 2. Start the next timer after waiting for the previous one\n const fast = resolveAfter1Second();\n console.log(await fast);\n\n console.log(\"== sequentialStart done ==\");\n}\n\nasync function sequentialWait() {\n console.log(\"== sequentialWait starts ==\");\n\n // 1. Start two timers without waiting for each other\n const slow = resolveAfter2Seconds();\n const fast = resolveAfter1Second();\n\n // 2. Wait for the slow timer to complete, and then log the result\n console.log(await slow);\n // 3. Wait for the fast timer to complete, and then log the result\n console.log(await fast);\n\n console.log(\"== sequentialWait done ==\");\n}\n\nasync function concurrent1() {\n console.log(\"== concurrent1 starts ==\");\n\n // 1. Start two timers concurrently and wait for both to complete\n const results = await Promise.all([\n resolveAfter2Seconds(),\n resolveAfter1Second(),\n ]);\n // 2. Log the results together\n console.log(results[0]);\n console.log(results[1]);\n\n console.log(\"== concurrent1 done ==\");\n}\n\nasync function concurrent2() {\n console.log(\"== concurrent2 starts ==\");\n\n // 1. Start two timers concurrently, log immediately after each one is done\n await Promise.all([\n (async () => console.log(await resolveAfter2Seconds()))(),\n (async () => console.log(await resolveAfter1Second()))(),\n ]);\n console.log(\"== concurrent2 done ==\");\n}\n\nsequentialStart(); // after 2 seconds, logs \"slow\", then after 1 more second, \"fast\"\n\n// wait above to finish\nsetTimeout(sequentialWait, 4000); // after 2 seconds, logs \"slow\" and then \"fast\"\n\n// wait again\nsetTimeout(concurrent1, 7000); // same as sequentialWait\n\n// wait again\nsetTimeout(concurrent2, 10000); // after 1 second, logs \"fast\", then after 1 more second, \"slow\"\n</code></pre></div>\n<h4 id=\"await_and_concurrency\">await and concurrency</h4>\n<p>In <code>sequentialStart</code>, execution suspends 2 seconds for the first\n<code>await</code>, and then another second for the second <code>await</code>. The\nsecond timer is not created until the first has already fired, so the code finishes\nafter 3 seconds.</p>\n<p>In <code>sequentialWait</code>, both timers are created and then <code>await</code>ed.\nThe timers run concurrently, which means the code finishes in 2 rather than 3 seconds,\ni.e. the slowest timer.\nHowever, the <code>await</code> calls still run in series, which means the second\n<code>await</code> will wait for the first one to finish. In this case, the result of\nthe fastest timer is processed after the slowest.</p>\n<p>If you wish to safely perform other jobs after two or more jobs run concurrently and are complete, you must await a call\nto <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all\"><code>Promise.all()</code></a> or <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/allSettled\"><code>Promise.allSettled()</code></a> before that job.</p>\n<div class=\"notecard warning\">\n<p><strong>Warning:</strong>\nThe functions <code>sequentialWait</code> and <code>concurrent1</code>\nare not functionally equivalent.</p>\n<p>In <code>sequentialWait</code>, if promise <code>fast</code> rejects before promise\n<code>slow</code> is fulfilled, then an unhandled promise rejection error will be\nraised, regardless of whether the caller has configured a catch clause.</p>\n<p>In <code>concurrent1</code>, <code>Promise.all</code> wires up the promise\nchain in one go, meaning that the operation will fail-fast regardless of the order of\nrejection of the promises, and the error will always occur within the configured\npromise chain, enabling it to be caught in the normal way.</p>\n</div>"}},{"type":"prose","value":{"id":"rewriting_a_promise_chain_with_an_async_function","title":"Rewriting a Promise chain with an async function","isH3":true,"content":"<p>An API that returns a <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise\"><code>Promise</code></a> will result in a promise chain, and it\nsplits the function into many parts. Consider the following code:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function getProcessedData(url) {\n return downloadData(url) // returns a promise\n .catch((e) => downloadFallbackData(url)) // returns a promise\n .then((v) => processDataInWorker(v)); // returns a promise\n}\n</code></pre></div>\n<p>it can be rewritten with a single async function as follows:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>async function getProcessedData(url) {\n let v;\n try {\n v = await downloadData(url);\n } catch (e) {\n v = await downloadFallbackData(url);\n }\n return processDataInWorker(v);\n}\n</code></pre></div>\n<p>Alternatively, you can chain the promise with <code>catch()</code>:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>async function getProcessedData(url) {\n const v = await downloadData(url).catch((e) => downloadFallbackData(url));\n return processDataInWorker(v);\n}\n</code></pre></div>\n<p>In the two rewritten versions, notice there is no <code>await</code> statement after the\n<code>return</code> keyword, although that would be valid too: The return value of an\nasync function is implicitly wrapped in <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/resolve\"><code>Promise.resolve</code></a> - if\nit's not already a promise itself (as in the examples).</p>"}},{"type":"specifications","value":{"id":"specifications","title":"Specifications","isH3":false,"specifications":[{"bcdSpecificationURL":"https://tc39.es/ecma262/multipage/ecmascript-language-functions-and-classes.html#sec-async-function-definitions","title":"ECMAScript® 2025 Language Specification"}],"query":"javascript.statements.async_function"}},{"type":"browser_compatibility","value":{"id":"browser_compatibility","title":"Browser compatibility","isH3":false,"query":"javascript.statements.async_function"}},{"type":"prose","value":{"id":"see_also","title":"See also","isH3":false,"content":"<ul>\n<li><a href=\"/en-US/docs/Web/JavaScript/Guide/Functions\">Functions</a> guide</li>\n<li><a href=\"/en-US/docs/Web/JavaScript/Guide/Using_promises\">Using promises</a> guide</li>\n<li><a href=\"/en-US/docs/Web/JavaScript/Reference/Functions\">Functions</a></li>\n<li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction\"><code>AsyncFunction</code></a></li>\n<li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/async_function\"><code>async function</code> expression</a></li>\n<li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/function\"><code>function</code></a></li>\n<li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/function*\"><code>function*</code></a></li>\n<li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/async_function*\"><code>async function*</code></a></li>\n<li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/await\"><code>await</code></a></li>\n<li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise\"><code>Promise</code></a></li>\n<li><a href=\"https://innolitics.com/10x/javascript-decorators-for-promise-returning-functions/\" class=\"external\" target=\"_blank\">Decorating async JavaScript functions</a> on innolitics.com (2016)</li>\n</ul>"}}],"isActive":true,"isMarkdown":true,"isTranslated":false,"locale":"en-US","mdn_url":"/en-US/docs/Web/JavaScript/Reference/Statements/async_function","modified":"2025-02-11T14:16:45.000Z","native":"English (US)","noIndexing":false,"other_translations":[{"locale":"de","title":"async function","native":"Deutsch"},{"locale":"es","title":"Función async","native":"Español"},{"locale":"fr","title":"async function","native":"Français"},{"locale":"ja","title":"async function","native":"日本語"},{"locale":"ko","title":"async function","native":"한국어"},{"locale":"pt-BR","title":"Funções assíncronas","native":"Português (do Brasil)"},{"locale":"ru","title":"async function","native":"Русский"},{"locale":"zh-CN","title":"async function","native":"中文 (简体)"},{"locale":"zh-TW","title":"async function","native":"正體中文 (繁體)"}],"pageTitle":"async function - JavaScript | MDN","parents":[{"uri":"/en-US/docs/Web","title":"References"},{"uri":"/en-US/docs/Web/JavaScript","title":"JavaScript"},{"uri":"/en-US/docs/Web/JavaScript/Reference","title":"Reference"},{"uri":"/en-US/docs/Web/JavaScript/Reference/Statements","title":"Statements and declarations"},{"uri":"/en-US/docs/Web/JavaScript/Reference/Statements/async_function","title":"async function"}],"popularity":null,"short_title":"async function","sidebarHTML":"<ol><li class=\"section\"><a href=\"/en-US/docs/Web/JavaScript\">JavaScript</a></li><li class=\"section\">Tutorials and guides</li><li class=\"toggle\"><details><summary>Beginner's tutorials</summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Your_first_website/Adding_interactivity\">Your first website: Adding interactivity</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting\">Dynamic scripting with JavaScript</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries\">JavaScript frameworks and libraries</a></li></ol></details></li><li class=\"toggle\"><details><summary>JavaScript Guide</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Introduction\">Introduction</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Grammar_and_types\">Grammar and types</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Control_flow_and_error_handling\">Control flow and error handling</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Loops_and_iteration\">Loops and iteration</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Functions\">Functions</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Expressions_and_operators\">Expressions and operators</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Numbers_and_strings\">Numbers and strings</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Representing_dates_times\">Representing dates & times</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Regular_expressions\">Regular expressions</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Indexed_collections\">Indexed collections</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Keyed_collections\">Keyed collections</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Working_with_objects\">Working with objects</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Using_classes\">Using classes</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Using_promises\">Using promises</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Typed_arrays\">JavaScript typed arrays</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Iterators_and_generators\">Iterators and generators</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Internationalization\">Internationalization</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Meta_programming\">Meta programming</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Guide/Modules\">JavaScript modules</a></li></ol></details></li><li class=\"toggle\"><details><summary>Intermediate</summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects\">Advanced JavaScript objects</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Async_JS\">Asynchronous JavaScript</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_APIs\">Client-side web APIs</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Language_overview\">Language overview</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Data_structures\">JavaScript data structures</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Equality_comparisons_and_sameness\">Equality comparisons and sameness</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_properties\">Enumerability and ownership of properties</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Closures\">Closures</a></li></ol></details></li><li class=\"toggle\"><details><summary>Advanced</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain\">Inheritance and the prototype chain</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Memory_management\">Memory Management</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Event_loop\">Concurrency model and Event Loop</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Web/JavaScript/Reference\">References</a></li><li class=\"toggle\"><details><summary>Built-in objects</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects\">Overview</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/AggregateError\">AggregateError</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array\">Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer\">ArrayBuffer</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction\">AsyncFunction</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncGenerator\">AsyncGenerator</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncGeneratorFunction\">AsyncGeneratorFunction</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncIterator\">AsyncIterator</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics\">Atomics</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt\">BigInt</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt64Array\">BigInt64Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigUint64Array\">BigUint64Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean\">Boolean</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView\">DataView</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date\">Date</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/decodeURI\">decodeURI()</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/decodeURIComponent\">decodeURIComponent()</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURI\">encodeURI()</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURIComponent\">encodeURIComponent()</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error\">Error</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/escape\">escape()</a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n<span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval\">eval()</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/EvalError\">EvalError</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/FinalizationRegistry\">FinalizationRegistry</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float16Array\">Float16Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float32Array\">Float32Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float64Array\">Float64Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function\">Function</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Generator\">Generator</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/GeneratorFunction\">GeneratorFunction</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/globalThis\">globalThis</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity\">Infinity</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int16Array\">Int16Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int32Array\">Int32Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int8Array\">Int8Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/InternalError\">InternalError</a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n<span class=\"visually-hidden\">Non-standard</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl\">Intl</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/isFinite\">isFinite()</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/isNaN\">isNaN()</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Iterator\">Iterator</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON\">JSON</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map\">Map</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math\">Math</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/NaN\">NaN</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number\">Number</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object\">Object</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseFloat\">parseFloat()</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt\">parseInt()</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise\">Promise</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy\">Proxy</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/RangeError\">RangeError</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/ReferenceError\">ReferenceError</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect\">Reflect</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp\">RegExp</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set\">Set</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer\">SharedArrayBuffer</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/String\">String</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol\">Symbol</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SyntaxError\">SyntaxError</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal\">Temporal</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n<span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray\">TypedArray</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError\">TypeError</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint16Array\">Uint16Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array\">Uint32Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array\">Uint8Array</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8ClampedArray\">Uint8ClampedArray</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined\">undefined</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/unescape\">unescape()</a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n<span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/URIError\">URIError</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap\">WeakMap</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakRef\">WeakRef</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet\">WeakSet</a></li></ol></details></li><li class=\"toggle\"><details><summary>Expressions & operators</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators\">Overview</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Addition\">Addition (+)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Addition_assignment\">Addition assignment (+=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Assignment\">Assignment (=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/async_function\">async function expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/async_function*\">async function* expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/await\">await</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_AND\">Bitwise AND (&)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_AND_assignment\">Bitwise AND assignment (&=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_NOT\">Bitwise NOT (~)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_OR\">Bitwise OR (|)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_OR_assignment\">Bitwise OR assignment (|=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_XOR\">Bitwise XOR (^)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_XOR_assignment\">Bitwise XOR assignment (^=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/class\">class expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Comma_operator\">Comma operator (,)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_operator\">Conditional (ternary) operator</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Decrement\">Decrement (--)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/delete\">delete</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment\">Destructuring assignment</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Division\">Division (/)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Division_assignment\">Division assignment (/=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Equality\">Equality (==)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Exponentiation\">Exponentiation (**)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Exponentiation_assignment\">Exponentiation assignment (**=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/function\">function expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/function*\">function* expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Greater_than\">Greater than (>)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Greater_than_or_equal\">Greater than or equal (>=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Grouping\">Grouping operator ( )</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/import.meta\">import.meta</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/import\">import()</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/in\">in</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Increment\">Increment (++)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Inequality\">Inequality (!=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/instanceof\">instanceof</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Left_shift\">Left shift (<<)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Left_shift_assignment\">Left shift assignment (<<=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Less_than\">Less than (<)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Less_than_or_equal\">Less than or equal (<=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Logical_AND\">Logical AND (&&)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Logical_AND_assignment\">Logical AND assignment (&&=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Logical_NOT\">Logical NOT (!)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Logical_OR\">Logical OR (||)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Logical_OR_assignment\">Logical OR assignment (||=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Multiplication\">Multiplication (*)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Multiplication_assignment\">Multiplication assignment (*=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/new\">new</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/new.target\">new.target</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/null\">null</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_assignment\">Nullish coalescing assignment (??=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing\">Nullish coalescing operator (??)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer\">Object initializer</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Operator_precedence\">Operator precedence</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining\">Optional chaining (?.)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Property_accessors\">Property accessors</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Remainder\">Remainder (%)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Remainder_assignment\">Remainder assignment (%=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Right_shift\">Right shift (>>)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Right_shift_assignment\">Right shift assignment (>>=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax\">Spread syntax (...)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Strict_equality\">Strict equality (===)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Strict_inequality\">Strict inequality (!==)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Subtraction\">Subtraction (-)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Subtraction_assignment\">Subtraction assignment (-=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/super\">super</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/this\">this</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/typeof\">typeof</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Unary_negation\">Unary negation (-)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Unary_plus\">Unary plus (+)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Unsigned_right_shift\">Unsigned right shift (>>>)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Unsigned_right_shift_assignment\">Unsigned right shift assignment (>>>=)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/void\">void operator</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/yield\">yield</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/yield*\">yield*</a></li></ol></details></li><li class=\"toggle\"><details open=\"\"><summary>Statements & declarations</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements\">Overview</a></li><li><em><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/async_function\" aria-current=\"page\">async function</a></em></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/async_function*\">async function*</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/block\">Block statement</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/break\">break</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/class\">class</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/const\">const</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/continue\">continue</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/debugger\">debugger</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/do...while\">do...while</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/Empty\">Empty statement</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/export\">export</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/Expression_statement\">Expression statement</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/for\">for</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/for-await...of\">for await...of</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/for...in\">for...in</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/for...of\">for...of</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/function\">function</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/function*\">function*</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/if...else\">if...else</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/import\">import</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/label\">Labeled statement</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/let\">let</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/return\">return</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/switch\">switch</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/throw\">throw</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/try...catch\">try...catch</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/var\">var</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/while\">while</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/with\">with</a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n<span class=\"visually-hidden\">Deprecated</span>\n</abbr></li></ol></details></li><li class=\"toggle\"><details><summary>Functions</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Functions\">Overview</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions\">Arrow function expressions</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters\">Default parameters</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Functions/get\">get</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Functions/Method_definitions\">Method definitions</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters\">Rest parameters</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Functions/set\">set</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Functions/arguments\">The arguments object</a></li></ol></details></li><li class=\"toggle\"><details><summary>Classes</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Classes\">Overview</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Classes/constructor\">constructor</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Classes/extends\">extends</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Classes/Private_properties\">Private properties</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Classes/Public_class_fields\">Public class fields</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Classes/static\">static</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Classes/Static_initialization_blocks\">Static initialization blocks</a></li></ol></details></li><li class=\"toggle\"><details><summary>Regular expressions</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions\">Overview</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Backreference\">Backreference: \\1, \\2</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Capturing_group\">Capturing group: (...)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Character_class_escape\">Character class escape: \\d, \\D, \\w, \\W, \\s, \\S</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Character_class\">Character class: [...], [^...]</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Character_escape\">Character escape: \\n, \\u{...}</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Disjunction\">Disjunction: |</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Input_boundary_assertion\">Input boundary assertion: ^, $</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Literal_character\">Literal character: a, b</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Lookahead_assertion\">Lookahead assertion: (?=...), (?!...)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Lookbehind_assertion\">Lookbehind assertion: (?<=...), (?<!...)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Modifier\">Modifier: (?ims-ims:...)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Named_backreference\">Named backreference: \\k<name></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Named_capturing_group\">Named capturing group: (?<name>...)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Non-capturing_group\">Non-capturing group: (?:...)</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Quantifier\">Quantifier: *, +, ?, {n}, {n,}, {n,m}</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Unicode_character_class_escape\">Unicode character class escape: \\p{...}, \\P{...}</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Wildcard\">Wildcard: .</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Word_boundary_assertion\">Word boundary assertion: \\b, \\B</a></li></ol></details></li><li class=\"toggle\"><details><summary>Errors</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors\">Overview</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Promise_any_all_rejected\">AggregateError: No Promise in Promise.any was resolved</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Property_access_denied\">Error: Permission denied to access property \"x\"</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Too_much_recursion\">InternalError: too much recursion</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Not_a_valid_code_point\">RangeError: argument is not a valid code point</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/BigInt_division_by_zero\">RangeError: BigInt division by zero</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/BigInt_negative_exponent\">RangeError: BigInt negative exponent</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Form_must_be_one_of\">RangeError: form must be one of 'NFC', 'NFD', 'NFKC', or 'NFKD'</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_array_length\">RangeError: invalid array length</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_date\">RangeError: invalid date</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Precision_range\">RangeError: precision is out of range</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_radix\">RangeError: radix must be an integer</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Resulting_string_too_large\">RangeError: repeat count must be less than infinity</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Negative_repetition_count\">RangeError: repeat count must be non-negative</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_be_converted_to_BigInt_because_it_isnt_an_integer\">RangeError: x can't be converted to BigInt because it isn't an integer</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Not_defined\">ReferenceError: \"x\" is not defined</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Undeclared_var\">ReferenceError: assignment to undeclared variable \"x\"</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_access_lexical_declaration_before_init\">ReferenceError: can't access lexical declaration 'X' before initialization</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Deprecated_caller_or_arguments_usage\">ReferenceError: deprecated caller or arguments usage</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Super_not_called\">ReferenceError: must call super constructor before using 'this' in derived class constructor</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Super_called_twice\">ReferenceError: super() called twice in derived class constructor</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_strict_arguments_eval\">SyntaxError: 'arguments'/'eval' can't be defined or assigned to in strict mode code</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Deprecated_octal_literal\">SyntaxError: \"0\"-prefixed octal literals are deprecated</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Strict_non_simple_params\">SyntaxError: \"use strict\" not allowed in function with non-simple parameters</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Reserved_identifier\">SyntaxError: \"x\" is a reserved identifier</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_backslash_at_end_of_pattern\">SyntaxError: \\ at end of pattern</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_for-of_initializer\">SyntaxError: a declaration in the head of a for-of loop can't have an initializer</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Delete_in_strict_mode\">SyntaxError: applying the 'delete' operator to an unqualified name is deprecated</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Arguments_not_allowed\">SyntaxError: arguments is not valid in fields</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_await\">SyntaxError: await is only valid in async functions, async generators and modules</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/await_yield_in_parameter\">SyntaxError: await/yield expression can't be used in parameter</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_use_nullish_coalescing_unparenthesized\">SyntaxError: cannot use `??` unparenthesized within `||` and `&&` expressions</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_character_class_escape_in_class_range\">SyntaxError: character class escape cannot be used in class range in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_continue\">SyntaxError: continue must be inside loop</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_duplicate_capture_group_name\">SyntaxError: duplicate capture group name in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Duplicate_parameter\">SyntaxError: duplicate formal argument x</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_for-in_initializer\">SyntaxError: for-in loop head declarations may not have initializers</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Unnamed_function_statement\">SyntaxError: function statement requires a name</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Function_label\">SyntaxError: functions cannot be labelled</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Either_be_both_static_or_non-static\">SyntaxError: getter and setter for private name #x should either be both static or non-static</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Getter_no_arguments\">SyntaxError: getter functions must have no arguments</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Identifier_after_number\">SyntaxError: identifier starts immediately after numeric literal</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Illegal_character\">SyntaxError: illegal character</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/import_decl_module_top_level\">SyntaxError: import declarations may only appear at top level of a module</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_incomplete_quantifier\">SyntaxError: incomplete quantifier in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_assignment_left-hand_side\">SyntaxError: invalid assignment left-hand side</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_BigInt_syntax\">SyntaxError: invalid BigInt syntax</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_capture_group_name\">SyntaxError: invalid capture group name in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_char_in_class\">SyntaxError: invalid character in class in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_class_set_operation\">SyntaxError: invalid class set operation in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_decimal_escape\">SyntaxError: invalid decimal escape in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_identity_escape\">SyntaxError: invalid identity escape in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_named_capture_reference\">SyntaxError: invalid named capture reference in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_property_name\">SyntaxError: invalid property name in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_range_in_character_class\">SyntaxError: invalid range in character class</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_group\">SyntaxError: invalid regexp group</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_regexp_flag\">SyntaxError: invalid regular expression flag \"x\"</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_invalid_unicode_escape\">SyntaxError: invalid unicode escape in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/JSON_bad_parse\">SyntaxError: JSON.parse: bad parsing</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Label_not_found\">SyntaxError: label not found</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Missing_colon_after_property_id\">SyntaxError: missing : after property id</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Missing_parenthesis_after_argument_list\">SyntaxError: missing ) after argument list</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Missing_parenthesis_after_condition\">SyntaxError: missing ) after condition</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Missing_bracket_after_list\">SyntaxError: missing ] after element list</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Missing_curly_after_function_body\">SyntaxError: missing } after function body</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Missing_curly_after_property_list\">SyntaxError: missing } after property list</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Missing_initializer_in_const\">SyntaxError: missing = in const declaration</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Missing_formal_parameter\">SyntaxError: missing formal parameter</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Missing_name_after_dot_operator\">SyntaxError: missing name after . operator</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/No_variable_name\">SyntaxError: missing variable name</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_negated_char_class_with_strings\">SyntaxError: negated character class with strings in regular expression</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_new_optional\">SyntaxError: new keyword cannot be used with an optional chain</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_nothing_to_repeat\">SyntaxError: nothing to repeat</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_numbers_out_of_order_in_quantifier\">SyntaxError: numbers out of order in {} quantifier.</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Deprecated_octal_escape_sequence\">SyntaxError: octal escape sequences can't be used in untagged template literals or in strict mode code</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Parameter_after_rest_parameter\">SyntaxError: parameter after rest parameter</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_delete_private_fields\">SyntaxError: private fields can't be deleted</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Duplicate_proto\">SyntaxError: property name __proto__ appears more than once in object literal</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Regex_raw_bracket\">SyntaxError: raw bracket is not allowed in regular expression with unicode flag</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Redeclared_parameter\">SyntaxError: redeclaration of formal parameter \"x\"</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Undeclared_private_field_or_method\">SyntaxError: reference to undeclared private field or method #x</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Rest_with_default\">SyntaxError: rest parameter may not have a default</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_return\">SyntaxError: return not in function</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Setter_one_argument\">SyntaxError: setter functions must have one argument</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/String_literal_EOL\">SyntaxError: string literal contains an unescaped line break</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_super_call\">SyntaxError: super() is only valid in derived class constructors</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_optional_template\">SyntaxError: tagged template cannot be used with optional chain</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Hash_outside_class\">SyntaxError: Unexpected '#' used outside of class body</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Unexpected_token\">SyntaxError: Unexpected token</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_break\">SyntaxError: unlabeled break must be inside loop or switch</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Unparenthesized_unary_expr_lhs_exponentiation\">SyntaxError: unparenthesized unary expression can't appear on the left-hand side of '**'</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Bad_super_prop\">SyntaxError: use of super property/member accesses only valid within methods or eval code within methods</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Deprecated_source_map_pragma\">SyntaxError: Using //@ to indicate sourceURL pragmas is deprecated. Use //# instead</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/is_not_iterable\">TypeError: 'x' is not iterable</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Unexpected_type\">TypeError: \"x\" is (not) \"y\"</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Not_a_constructor\">TypeError: \"x\" is not a constructor</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Not_a_function\">TypeError: \"x\" is not a function</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/No_non-null_object\">TypeError: \"x\" is not a non-null object</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Read-only\">TypeError: \"x\" is read-only</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/BigInt_not_serializable\">TypeError: BigInt value can't be serialized in JSON</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Builtin_ctor_no_new\">TypeError: calling a builtin X constructor without new is forbidden</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Get_set_missing_private\">TypeError: can't access/set private field or method: object is not the right class</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_assign_to_property\">TypeError: can't assign to property \"x\" on \"y\": not an object</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_convert_BigInt_to_number\">TypeError: can't convert BigInt to number</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_convert_x_to_BigInt\">TypeError: can't convert x to BigInt</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_define_property_object_not_extensible\">TypeError: can't define property \"x\": \"obj\" is not extensible</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Non_configurable_array_element\">TypeError: can't delete non-configurable array element</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_redefine_property\">TypeError: can't redefine non-configurable property \"x\"</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_set_prototype\">TypeError: can't set prototype of this object</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cyclic_prototype\">TypeError: can't set prototype: it would cause a prototype chain cycle</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/in_operator_no_object\">TypeError: cannot use 'in' operator to search for 'x' in 'y'</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Class_ctor_no_new\">TypeError: class constructors must be invoked with 'new'</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cyclic_object_value\">TypeError: cyclic object value</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_derived_return\">TypeError: derived class constructor returned invalid value x</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Private_setter_only\">TypeError: getting private setter-only property</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Private_double_initialization\">TypeError: Initializing an object twice is an error with private fields/methods</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/invalid_right_hand_side_instanceof_operand\">TypeError: invalid 'instanceof' operand 'x'</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Array_sort_argument\">TypeError: invalid Array.prototype.sort argument</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_const_assignment\">TypeError: invalid assignment to const \"x\"</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Constructor_cant_be_used_directly\">TypeError: Iterator/AsyncIterator constructor can't be used directly</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Requires_global_RegExp\">TypeError: matchAll/replaceAll must be called with a global RegExp</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/More_arguments_needed\">TypeError: More arguments needed</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/No_properties\">TypeError: null/undefined has no properties</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Cant_delete\">TypeError: property \"x\" is non-configurable and can't be deleted</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Reduce_of_empty_array_with_no_initial_value\">TypeError: Reduce of empty array with no initial value</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Getter_only\">TypeError: setting getter-only property \"x\"</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Key_not_weakly_held\">TypeError: WeakSet key/WeakMap value 'x' must be an object or an unregistered symbol</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Called_on_incompatible_type\">TypeError: X.prototype.y called on incompatible type</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Malformed_URI\">URIError: malformed URI sequence</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Already_has_pragma\">Warning: -file- is being assigned a //# sourceMappingURL, but already has one</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Errors/Stmt_after_return\">Warning: unreachable code after return statement</a></li></ol></details></li><li class=\"toggle\"><details><summary>Misc</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/JavaScript_technologies_overview\">JavaScript technologies overview</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Lexical_grammar\">Lexical grammar</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Iteration_protocols\">Iteration protocols</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Strict_mode\">Strict mode</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Template_literals\">Template literals</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Trailing_commas\">Trailing commas</a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Deprecated_and_obsolete_features\">Deprecated features</a></li></ol></details></li></ol>","source":{"folder":"en-us/web/javascript/reference/statements/async_function","github_url":"https://github.com/mdn/content/blob/main/files/en-us/web/javascript/reference/statements/async_function/index.md","last_commit_url":"https://github.com/mdn/content/commit/2982fcbb31c65f324a80fd9cec516a81d4793cd4","filename":"index.md"},"summary":"The async function declaration creates a binding of a new async function to a given name. The await keyword is permitted within the function body, enabling asynchronous, promise-based behavior to be written in a cleaner style and avoiding the need to explicitly configure promise chains.","title":"async function","toc":[{"text":"Try it","id":"try_it"},{"text":"Syntax","id":"syntax"},{"text":"Description","id":"description"},{"text":"Examples","id":"examples"},{"text":"Specifications","id":"specifications"},{"text":"Browser compatibility","id":"browser_compatibility"},{"text":"See also","id":"see_also"}],"baseline":{"baseline":"high","baseline_low_date":"2017-04-05","baseline_high_date":"2019-10-05","support":{"chrome":"55","chrome_android":"55","edge":"15","firefox":"52","firefox_android":"52","safari":"10.1","safari_ios":"10.3"}},"browserCompat":["javascript.statements.async_function"],"pageType":"javascript-statement"}}</script></body></html>