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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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#description">Description</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#constructor">Constructor</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#static_methods">Static methods</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_properties">Instance properties</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_methods">Instance methods</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#examples">Examples</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#specifications">Specifications</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#browser_compatibility">Browser compatibility</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#see_also">See also</a></li> </ul> </section> </div> </div> <div class="sidebar-body"> <ol> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">Standard built-in objects</a></li> <li class="section"><em><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB" aria-current="page"><code>Object</code></a></em></li> <li> <details open> <summary>Constructor</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object() constructor</code></a></li> </ol> </details></li> <li> <details open> <summary>Static methods</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.assign()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.create()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.defineProperties()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.defineProperty()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.entries()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.freeze()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.fromEntries()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptor?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getOwnPropertyDescriptor()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptors?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getOwnPropertyDescriptors()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getOwnPropertyNames()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getOwnPropertySymbols()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getPrototypeOf()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/groupBy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.groupBy()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwn?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.hasOwn()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.is()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isExtensible?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.isExtensible()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isFrozen?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.isFrozen()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isSealed?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.isSealed()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.keys()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/preventExtensions?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.preventExtensions()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/seal?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.seal()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.setPrototypeOf()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/values?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.values()</code></a></li> </ol> </details></li> <li> <details open> <summary>Instance methods</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__defineGetter__()</code></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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineSetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__defineSetter__()</code></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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupGetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__lookupGetter__()</code></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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupSetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__lookupSetter__()</code></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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.hasOwnProperty()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.isPrototypeOf()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.propertyIsEnumerable()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.toLocaleString()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.toString()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.valueOf()</code></a></li> </ol> </details></li> <li> <details open> <summary>Instance properties</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.constructor</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__proto__</code></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="section no-link">Inheritance</li> <li class="section"><em><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB" aria-current="page"><code>Object/Function</code></a></em></li> <li> <details> <summary>Static methods</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.apply()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.bind()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.call()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/Symbol.hasInstance?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype[Symbol.hasInstance]()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/toString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.toString()</code></a></li> </ol> </details></li> <li> <details> <summary>Static properties</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/arguments?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.arguments</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/caller?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.caller</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/displayName?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function: displayName</code></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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/length?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function: length</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/name?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function: name</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/prototype?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function: prototype</code></a></li> </ol> </details></li> <li> <details> <summary>Instance methods</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__defineGetter__()</code></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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineSetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__defineSetter__()</code></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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupGetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__lookupGetter__()</code></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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupSetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__lookupSetter__()</code></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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.hasOwnProperty()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.isPrototypeOf()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.propertyIsEnumerable()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.toLocaleString()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.toString()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.valueOf()</code></a></li> </ol> </details></li> <li> <details> <summary>Instance properties</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.constructor</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__proto__</code></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> </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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#description">Description</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#constructor">Constructor</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#static_methods">Static methods</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_properties">Instance properties</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_methods">Instance methods</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#examples">Examples</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#specifications">Specifications</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#browser_compatibility">Browser compatibility</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#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>Object</h1> <details class="baseline-indicator high"> <summary><span class="indicator" role="img" aria-label="Baseline Check"></span><h2>Baseline <span class="not-bold">Widely available</span></h2> <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 July 2015.</p> <ul> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Glossary/Baseline/Compatibility?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB" data-glean="baseline_link_learn_more" target="_blank" class="learn-more">Learn more</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#browser_compatibility" data-glean="baseline_link_bcd_table">See full compatibility</a></li> <li><a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://survey.alchemer.com/s3/7634825/MDN-baseline-feedback?page%3D%252Fen-US%252Fdocs%252FWeb%252FJavaScript%252FReference%252FGlobal_Objects%252FObject%26level%3Dhigh" 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>Object</code></strong> type represents one of <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Data_structures?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">JavaScript's data types</a>. It is used to store various keyed collections and more complex entities. Objects can be created using the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object()</code></a> constructor or the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">object initializer / literal syntax</a>.</p> </div> <section aria-labelledby="description"> <h2 id="description"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#description">Description</a></h2> <div class="section-content"> <p>Nearly all <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Data_structures?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#objects">objects</a> in JavaScript are instances of <code>Object</code>; a typical object inherits properties (including methods) from <code>Object.prototype</code>, although these properties may be shadowed (a.k.a. overridden). The only objects that don't inherit from <code>Object.prototype</code> are those with <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#null-prototype_objects"><code>null</code> prototype</a>, or descended from other <code>null</code> prototype objects.</p> <p>Changes to the <code>Object.prototype</code> object are seen by <strong>all</strong> objects through prototype chaining, unless the properties and methods subject to those changes are overridden further along the prototype chain. This provides a very powerful although potentially dangerous mechanism to override or extend object behavior. To make it more secure, <code>Object.prototype</code> is the only object in the core JavaScript language that has <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#description">immutable prototype</a> — the prototype of <code>Object.prototype</code> is always <code>null</code> and not changeable.</p> </div> </section> <section aria-labelledby="object_prototype_properties"> <h3 id="object_prototype_properties"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#object_prototype_properties">Object prototype properties</a></h3> <div class="section-content"> <p>You should avoid calling any <code>Object.prototype</code> method directly from the instance, especially those that are not intended to be polymorphic (i.e. only its initial behavior makes sense and no descending object could override it in a meaningful way). All objects descending from <code>Object.prototype</code> may define a custom own property that has the same name, but with entirely different semantics from what you expect. Furthermore, these properties are not inherited by <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#null-prototype_objects"><code>null</code>-prototype objects</a>. All modern JavaScript utilities for working with objects are <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#static_methods">static</a>. More specifically:</p> <ul> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>valueOf()</code></a>, <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>toString()</code></a>, and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>toLocaleString()</code></a> exist to be polymorphic and you should expect the object to define its own implementation with sensible behaviors, so you can call them as instance methods. However, <code>valueOf()</code> and <code>toString()</code> are usually implicitly called through <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Data_structures?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#type_coercion">type conversion</a> and you don't need to call them yourself in your code.</li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>__defineGetter__()</code></a>, <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineSetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>__defineSetter__()</code></a>, <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupGetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>__lookupGetter__()</code></a>, and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupSetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>__lookupSetter__()</code></a> are deprecated and should not be used. Use the static alternatives <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.defineProperty()</code></a> and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptor?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getOwnPropertyDescriptor()</code></a> instead.</li> <li>The <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>__proto__</code></a> property is deprecated and should not be used. The <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getPrototypeOf()</code></a> and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.setPrototypeOf()</code></a> alternatives are static methods.</li> <li>The <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>propertyIsEnumerable()</code></a> and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>hasOwnProperty()</code></a> methods can be replaced with the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptor?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getOwnPropertyDescriptor()</code></a> and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwn?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.hasOwn()</code></a> static methods, respectively.</li> <li>The <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>isPrototypeOf()</code></a> method can usually be replaced with <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/instanceof?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>instanceof</code></a>, if you are checking the <code>prototype</code> property of a constructor.</li> </ul> <p>In case where a semantically equivalent static method doesn't exist, or if you really want to use the <code>Object.prototype</code> method, you should directly <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>call()</code></a> the <code>Object.prototype</code> method on your target object instead, to prevent the object from having an overriding property that produces unexpected results.</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const obj = { foo: 1, // You should not define such a method on your own object, // but you may not be able to prevent it from happening if // you are receiving the object from external input propertyIsEnumerable() { return false; }, }; obj.propertyIsEnumerable("foo"); // false; unexpected result Object.prototype.propertyIsEnumerable.call(obj, "foo"); // true; expected result </code></pre> </div> </div> </section> <section aria-labelledby="deleting_a_property_from_an_object"> <h3 id="deleting_a_property_from_an_object"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#deleting_a_property_from_an_object">Deleting a property from an object</a></h3> <div class="section-content"> <p>There isn't any method in an Object itself to delete its own properties (such as <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/delete?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Map.prototype.delete()</code></a>). To do so, one must use the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/delete?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>delete</code></a> operator.</p> </div> </section> <section aria-labelledby="null-prototype_objects"> <h3 id="null-prototype_objects"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#null-prototype_objects">null-prototype objects</a></h3> <div class="section-content"> <p>Almost all objects in JavaScript ultimately inherit from <code>Object.prototype</code> (see <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">inheritance and the prototype chain</a>). However, you may create <code>null</code>-prototype objects using <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.create(null)</code></a> or the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">object initializer syntax</a> with <code>__proto__: null</code> (note: the <code>__proto__</code> key in object literals is different from the deprecated <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__proto__</code></a> property). You can also change the prototype of an existing object to <code>null</code> by calling <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.setPrototypeOf(obj, null)</code></a>.</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const obj = Object.create(null); const obj2 = { __proto__: null }; </code></pre> </div> <p>An object with a <code>null</code> prototype can behave in unexpected ways, because it doesn't inherit any object methods from <code>Object.prototype</code>. This is especially true when debugging, since common object-property converting/detecting utility functions may generate errors, or lose information (especially if using silent error-traps that ignore errors).</p> <p>For example, the lack of <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.toString()</code></a> often makes debugging intractable:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const normalObj = {}; // create a normal object const nullProtoObj = Object.create(null); // create an object with "null" prototype console.log(`normalObj is: ${normalObj}`); // shows "normalObj is: [object Object]" console.log(`nullProtoObj is: ${nullProtoObj}`); // throws error: Cannot convert object to primitive value alert(normalObj); // shows [object Object] alert(nullProtoObj); // throws error: Cannot convert object to primitive value </code></pre> </div> <p>Other methods will fail as well.</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>normalObj.valueOf(); // shows {} nullProtoObj.valueOf(); // throws error: nullProtoObj.valueOf is not a function normalObj.hasOwnProperty("p"); // shows "true" nullProtoObj.hasOwnProperty("p"); // throws error: nullProtoObj.hasOwnProperty is not a function normalObj.constructor; // shows "Object() { [native code] }" nullProtoObj.constructor; // shows "undefined" </code></pre> </div> <p>We can add the <code>toString</code> method back to the null-prototype object by assigning it one:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>nullProtoObj.toString = Object.prototype.toString; // since new object lacks toString, add the original generic one back console.log(nullProtoObj.toString()); // shows "[object Object]" console.log(`nullProtoObj is: ${nullProtoObj}`); // shows "nullProtoObj is: [object Object]" </code></pre> </div> <p>Unlike normal objects, in which <code>toString()</code> is on the object's prototype, the <code>toString()</code> method here is an own property of <code>nullProtoObj</code>. This is because <code>nullProtoObj</code> has no (<code>null</code>) prototype.</p> <p>You can also revert a null-prototype object back to an ordinary object using <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.setPrototypeOf(nullProtoObj, Object.prototype)</code></a>.</p> <p>In practice, objects with <code>null</code> prototype are usually used as a cheap substitute for <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">maps</a>. The presence of <code>Object.prototype</code> properties will cause some bugs:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const ages = { alice: 18, bob: 27 }; function hasPerson(name) { return name in ages; } function getAge(name) { return ages[name]; } hasPerson("hasOwnProperty"); // true getAge("toString"); // [Function: toString] </code></pre> </div> <p>Using a null-prototype object removes this hazard without introducing too much complexity to the <code>hasPerson</code> and <code>getAge</code> functions:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const ages = Object.create(null, { alice: { value: 18, enumerable: true }, bob: { value: 27, enumerable: true }, }); hasPerson("hasOwnProperty"); // false getAge("toString"); // undefined </code></pre> </div> <p>In such case, the addition of any method should be done cautiously, as they can be confused with the other key-value pairs stored as data.</p> <p>Making your object not inherit from <code>Object.prototype</code> also prevents prototype pollution attacks. If a malicious script adds a property to <code>Object.prototype</code>, it will be accessible on every object in your program, except objects that have null prototype.</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const user = {}; // A malicious script: Object.prototype.authenticated = true; // Unexpectedly allowing unauthenticated user to pass through if (user.authenticated) { // access confidential data } </code></pre> </div> <p>JavaScript also has built-in APIs that produce <code>null</code>-prototype objects, especially those that use objects as ad hoc key-value collections. For example:</p> <ul> <li>The return value of <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/groupBy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.groupBy()</code></a></li> <li>The <code>groups</code> and <code>indices.groups</code> properties of the result of <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>RegExp.prototype.exec()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Symbol.unscopables?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Array.prototype[Symbol.unscopables]</code></a> (all <code>[Symbol.unscopables]</code> objects should have <code>null</code>-prototype)</li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/import.meta?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>import.meta</code></a></li> <li>Module namespace objects, obtained through <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Statements/import?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#namespace_import"><code>import * as ns from "module";</code></a> or <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/import?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>import()</code></a></li> </ul> <p>The term "<code>null</code>-prototype object" often also includes any object without <code>Object.prototype</code> in its prototype chain. Such objects can be created with <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Classes/extends?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#extending_null"><code>extends null</code></a> when using classes.</p> </div> </section> <section aria-labelledby="object_coercion"> <h3 id="object_coercion"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#object_coercion">Object coercion</a></h3> <div class="section-content"> <p>Many built-in operations that expect objects first coerce their arguments to objects. <a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://tc39.es/ecma262/multipage/abstract-operations.html%23sec-toobject" class="external" target="_blank">The operation</a> can be summarized as follows:</p> <ul> <li>Objects are returned as-is.</li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>undefined</code></a> and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/null?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>null</code></a> throw a <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>TypeError</code></a>.</li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Number</code></a>, <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/String?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>String</code></a>, <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Boolean</code></a>, <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Symbol</code></a>, <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>BigInt</code></a> primitives are wrapped into their corresponding object wrappers.</li> </ul> <p>There are two ways to achieve nearly the same effect in JavaScript.</p> <ul> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.valueOf()</code></a>: <code>Object.prototype.valueOf.call(x)</code> does exactly the object coercion steps explained above to convert <code>x</code>.</li> <li>The <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object()</code></a> function: <code>Object(x)</code> uses the same algorithm to convert <code>x</code>, except that <code>undefined</code> and <code>null</code> don't throw a <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>TypeError</code></a>, but return a plain object.</li> </ul> <p>Places that use object coercion include:</p> <ul> <li>The <code>object</code> parameter of <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Statements/for...in?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>for...in</code></a> loops.</li> <li>The <code>this</code> value of <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Array</code></a> methods.</li> <li>Parameters of <code>Object</code> methods such as <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.keys()</code></a>.</li> <li>Auto-boxing when a property is accessed on a primitive value, since primitives do not have properties.</li> <li>The <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/this?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>this</code></a> value when calling a non-strict function. Primitives are boxed while <code>null</code> and <code>undefined</code> are replaced with the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Glossary/Global_object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">global object</a>.</li> </ul> <p>Unlike <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Data_structures?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#primitive_coercion">conversion to primitives</a>, the object coercion process itself is not observable in any way, since it doesn't invoke custom code like <code>toString</code> or <code>valueOf</code> methods.</p> </div> </section> <section aria-labelledby="constructor"> <h2 id="constructor"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#constructor">Constructor</a></h2> <div class="section-content"> <dl> <dt id="object"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object()</code></a> </dt> <dd> <p>Turns the input into an object.</p> </dd> </dl> </div> </section> <section aria-labelledby="static_methods"> <h2 id="static_methods"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#static_methods">Static methods</a></h2> <div class="section-content"> <dl> <dt id="object.assign"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.assign()</code></a> </dt> <dd> <p>Copies the values of all enumerable own properties from one or more source objects to a target object.</p> </dd> <dt id="object.create"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.create()</code></a> </dt> <dd> <p>Creates a new object with the specified prototype object and properties.</p> </dd> <dt id="object.defineproperties"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.defineProperties()</code></a> </dt> <dd> <p>Adds the named properties described by the given descriptors to an object.</p> </dd> <dt id="object.defineproperty"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.defineProperty()</code></a> </dt> <dd> <p>Adds the named property described by a given descriptor to an object.</p> </dd> <dt id="object.entries"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.entries()</code></a> </dt> <dd> <p>Returns an array containing all of the <code>[key, value]</code> pairs of a given object's <strong>own</strong> enumerable string properties.</p> </dd> <dt id="object.freeze"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.freeze()</code></a> </dt> <dd> <p>Freezes an object. Other code cannot delete or change its properties.</p> </dd> <dt id="object.fromentries"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.fromEntries()</code></a> </dt> <dd> <p>Returns a new object from an iterable of <code>[key, value]</code> pairs. (This is the reverse of <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.entries</code></a>).</p> </dd> <dt id="object.getownpropertydescriptor"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptor?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getOwnPropertyDescriptor()</code></a> </dt> <dd> <p>Returns a property descriptor for a named property on an object.</p> </dd> <dt id="object.getownpropertydescriptors"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptors?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getOwnPropertyDescriptors()</code></a> </dt> <dd> <p>Returns an object containing all own property descriptors for an object.</p> </dd> <dt id="object.getownpropertynames"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getOwnPropertyNames()</code></a> </dt> <dd> <p>Returns an array containing the names of all of the given object's <strong>own</strong> enumerable and non-enumerable properties.</p> </dd> <dt id="object.getownpropertysymbols"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getOwnPropertySymbols()</code></a> </dt> <dd> <p>Returns an array of all symbol properties found directly upon a given object.</p> </dd> <dt id="object.getprototypeof"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.getPrototypeOf()</code></a> </dt> <dd> <p>Returns the prototype (internal <code>[[Prototype]]</code> property) of the specified object.</p> </dd> <dt id="object.groupby"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/groupBy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.groupBy()</code></a> </dt> <dd> <p>Groups the elements of a given iterable according to the string values returned by a provided callback function. The returned object has separate properties for each group, containing arrays with the elements in the group.</p> </dd> <dt id="object.hasown"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwn?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.hasOwn()</code></a> </dt> <dd> <p>Returns <code>true</code> if the specified object has the indicated property as its <em>own</em> property, or <code>false</code> if the property is inherited or does not exist.</p> </dd> <dt id="object.is"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.is()</code></a> </dt> <dd> <p>Compares if two values are the same value. Equates all <code>NaN</code> values (which differs from both <code>IsLooselyEqual</code> used by <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/Equality?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>==</code></a> and <code>IsStrictlyEqual</code> used by <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/Strict_equality?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>===</code></a>).</p> </dd> <dt id="object.isextensible"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isExtensible?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.isExtensible()</code></a> </dt> <dd> <p>Determines if extending of an object is allowed.</p> </dd> <dt id="object.isfrozen"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isFrozen?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.isFrozen()</code></a> </dt> <dd> <p>Determines if an object was frozen.</p> </dd> <dt id="object.issealed"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isSealed?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.isSealed()</code></a> </dt> <dd> <p>Determines if an object is sealed.</p> </dd> <dt id="object.keys"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.keys()</code></a> </dt> <dd> <p>Returns an array containing the names of all of the given object's <strong>own</strong> enumerable string properties.</p> </dd> <dt id="object.preventextensions"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/preventExtensions?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.preventExtensions()</code></a> </dt> <dd> <p>Prevents any extensions of an object.</p> </dd> <dt id="object.seal"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/seal?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.seal()</code></a> </dt> <dd> <p>Prevents other code from deleting properties of an object.</p> </dd> <dt id="object.setprototypeof"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.setPrototypeOf()</code></a> </dt> <dd> <p>Sets the object's prototype (its internal <code>[[Prototype]]</code> property).</p> </dd> <dt id="object.values"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/values?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.values()</code></a> </dt> <dd> <p>Returns an array containing the values that correspond to all of a given object's <strong>own</strong> enumerable string properties.</p> </dd> </dl> </div> </section> <section aria-labelledby="instance_properties"> <h2 id="instance_properties"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_properties">Instance properties</a></h2> <div class="section-content"> <p>These properties are defined on <code>Object.prototype</code> and shared by all <code>Object</code> instances.</p> <dl> <dt id="object.prototype.__proto__"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__proto__</code></a> <abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr> </dt> <dd> <p>Points to the object which was used as prototype when the object was instantiated.</p> </dd> <dt id="object.prototype.constructor"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.constructor</code></a> </dt> <dd> <p>The constructor function that created the instance object. For plain <code>Object</code> instances, the initial value is the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object</code></a> constructor. Instances of other constructors each inherit the <code>constructor</code> property from their respective <code>Constructor.prototype</code> object.</p> </dd> </dl> </div> </section> <section aria-labelledby="instance_methods"> <h2 id="instance_methods"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_methods">Instance methods</a></h2> <div class="section-content"> <dl> <dt id="object.prototype.__definegetter__"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__defineGetter__()</code></a> <abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr> </dt> <dd> <p>Associates a function with a property that, when accessed, executes that function and returns its return value.</p> </dd> <dt id="object.prototype.__definesetter__"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineSetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__defineSetter__()</code></a> <abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr> </dt> <dd> <p>Associates a function with a property that, when set, executes that function which modifies the property.</p> </dd> <dt id="object.prototype.__lookupgetter__"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupGetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__lookupGetter__()</code></a> <abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr> </dt> <dd> <p>Returns the function bound as a getter to the specified property.</p> </dd> <dt id="object.prototype.__lookupsetter__"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupSetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__lookupSetter__()</code></a> <abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr> </dt> <dd> <p>Returns the function bound as a setter to the specified property.</p> </dd> <dt id="object.prototype.hasownproperty"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.hasOwnProperty()</code></a> </dt> <dd> <p>Returns a boolean indicating whether an object contains the specified property as a direct property of that object and not inherited through the prototype chain.</p> </dd> <dt id="object.prototype.isprototypeof"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.isPrototypeOf()</code></a> </dt> <dd> <p>Returns a boolean indicating whether the object this method is called upon is in the prototype chain of the specified object.</p> </dd> <dt id="object.prototype.propertyisenumerable"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.propertyIsEnumerable()</code></a> </dt> <dd> <p>Returns a boolean indicating whether the specified property is the object's <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_properties?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">enumerable own</a> property.</p> </dd> <dt id="object.prototype.tolocalestring"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.toLocaleString()</code></a> </dt> <dd> <p>Calls <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>toString()</code></a>.</p> </dd> <dt id="object.prototype.tostring"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.toString()</code></a> </dt> <dd> <p>Returns a string representation of the object.</p> </dd> <dt id="object.prototype.valueof"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.valueOf()</code></a> </dt> <dd> <p>Returns the primitive value of the specified object.</p> </dd> </dl> </div> </section> <section aria-labelledby="examples"> <h2 id="examples"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#examples">Examples</a></h2> <div class="section-content"></div> </section> <section aria-labelledby="constructing_empty_objects"> <h3 id="constructing_empty_objects"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#constructing_empty_objects">Constructing empty objects</a></h3> <div class="section-content"> <p>The following example creates empty objects using the <code>new</code> keyword with different arguments:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const o1 = new Object(); const o2 = new Object(undefined); const o3 = new Object(null); </code></pre> </div> </div> </section> <section aria-labelledby="using_object_constructor_to_turn_primitives_into_an_object_of_their_respective_type"> <h3 id="using_object_constructor_to_turn_primitives_into_an_object_of_their_respective_type"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#using_object_constructor_to_turn_primitives_into_an_object_of_their_respective_type">Using Object() constructor to turn primitives into an Object of their respective type</a></h3> <div class="section-content"> <p>You can use the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object()</code></a> constructor to create an object wrapper of a primitive value.</p> <p>The following examples create variables <code>o1</code> and <code>o2</code> which are objects storing <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Boolean</code></a> and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>BigInt</code></a> values:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>// Equivalent to const o1 = new Boolean(true) const o1 = new Object(true); // No equivalent because BigInt() can't be called as a constructor, // and calling it as a regular function won't create an object const o2 = new Object(1n); </code></pre> </div> </div> </section> <section aria-labelledby="object_prototypes"> <h3 id="object_prototypes"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#object_prototypes">Object prototypes</a></h3> <div class="section-content"> <p>When altering the behavior of existing <code>Object.prototype</code> methods, consider injecting code by wrapping your extension before or after the existing logic. For example, this (untested) code will pre-conditionally execute custom logic before the built-in logic or someone else's extension is executed.</p> <p>When modifying prototypes with hooks, pass <code>this</code> and the arguments (the call state) to the current behavior by calling <code>apply()</code> on the function. This pattern can be used for any prototype, such as <code>Node.prototype</code>, <code>Function.prototype</code>, etc.</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const current = Object.prototype.valueOf; // Since my property "-prop-value" is cross-cutting and isn't always // on the same prototype chain, I want to modify Object.prototype: Object.prototype.valueOf = function (...args) { if (Object.hasOwn(this, "-prop-value")) { return this["-prop-value"]; } else { // It doesn't look like one of my objects, so let's fall back on // the default behavior by reproducing the current behavior as best we can. // The apply behaves like "super" in some other languages. // Even though valueOf() doesn't take arguments, some other hook may. return current.apply(this, args); } }; </code></pre> </div> <div class="notecard warning"> <p><strong>Warning:</strong> Modifying the <code>prototype</code> property of any built-in constructor is considered a bad practice and risks forward compatibility.</p> </div> <p>You can read more about prototypes in <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">Inheritance and the prototype chain</a>.</p> </div> </section> <h2 id="specifications"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#specifications">Specifications</a></h2> <table class="standard-table"> <thead> <tr> <th scope="col">Specification</th> </tr> </thead> <tbody> <tr> <td><a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://tc39.es/ecma262/multipage/fundamental-objects.html%23sec-object-objects">ECMAScript Language Specification <br><small># sec-object-objects</small></a></td> </tr> </tbody> </table> <h2 id="browser_compatibility"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#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="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#see_also">See also</a></h2> <div class="section-content"> <ul> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">Object initializer</a></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 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Content available under <a href="https://developer-mozilla-org.translate.goog/en-US/docs/MDN/Writing_guidelines/Attrib_copyright_license?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">a Creative Commons license</a>.</p> </div> </div> </footer> </div> <script type="application/json" id="hydration">{"url":"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object","doc":{"isMarkdown":true,"isTranslated":false,"isActive":true,"flaws":{},"title":"Object","mdn_url":"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object","locale":"en-US","native":"English (US)","browserCompat":["javascript.builtins.Object"],"baseline":{"baseline":"high","baseline_high_date":"2018-01-29","baseline_low_date":"2015-07-29","support":{"chrome":"1","chrome_android":"18","edge":"12","firefox":"1","firefox_android":"4","safari":"1","safari_ios":"1"}},"sidebarHTML":"<ol><li class=\"section\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects\">Standard built-in objects</a></li><li class=\"section\"><em><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object\" aria-current=\"page\"><code>Object</code></a></em></li><li><details open=\"\"><summary>Constructor</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object\"><code>Object() constructor</code></a></li></ol></details></li><li><details open=\"\"><summary>Static methods</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign\"><code>Object.assign()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create\"><code>Object.create()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties\"><code>Object.defineProperties()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty\"><code>Object.defineProperty()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries\"><code>Object.entries()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze\"><code>Object.freeze()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries\"><code>Object.fromEntries()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptor\"><code>Object.getOwnPropertyDescriptor()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptors\"><code>Object.getOwnPropertyDescriptors()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames\"><code>Object.getOwnPropertyNames()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols\"><code>Object.getOwnPropertySymbols()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getPrototypeOf\"><code>Object.getPrototypeOf()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/groupBy\"><code>Object.groupBy()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwn\"><code>Object.hasOwn()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is\"><code>Object.is()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isExtensible\"><code>Object.isExtensible()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isFrozen\"><code>Object.isFrozen()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isSealed\"><code>Object.isSealed()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys\"><code>Object.keys()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/preventExtensions\"><code>Object.preventExtensions()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/seal\"><code>Object.seal()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf\"><code>Object.setPrototypeOf()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/values\"><code>Object.values()</code></a></li></ol></details></li><li><details open=\"\"><summary>Instance methods</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__\"><code>Object.prototype.__defineGetter__()</code></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/Object/__defineSetter__\"><code>Object.prototype.__defineSetter__()</code></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/Object/__lookupGetter__\"><code>Object.prototype.__lookupGetter__()</code></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/Object/__lookupSetter__\"><code>Object.prototype.__lookupSetter__()</code></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/Object/hasOwnProperty\"><code>Object.prototype.hasOwnProperty()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf\"><code>Object.prototype.isPrototypeOf()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable\"><code>Object.prototype.propertyIsEnumerable()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString\"><code>Object.prototype.toLocaleString()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString\"><code>Object.prototype.toString()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf\"><code>Object.prototype.valueOf()</code></a></li></ol></details></li><li><details open=\"\"><summary>Instance properties</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor\"><code>Object.prototype.constructor</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto\"><code>Object.prototype.__proto__</code></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=\"section no-link\">Inheritance</li><li class=\"section\"><em><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object\" aria-current=\"page\"><code>Object/Function</code></a></em></li><li><details><summary>Static methods</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply\"><code>Function.prototype.apply()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind\"><code>Function.prototype.bind()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call\"><code>Function.prototype.call()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/Symbol.hasInstance\"><code>Function.prototype[Symbol.hasInstance]()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/toString\"><code>Function.prototype.toString()</code></a></li></ol></details></li><li><details><summary>Static properties</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/arguments\"><code>Function.prototype.arguments</code></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><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/Function/caller\"><code>Function.prototype.caller</code></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><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/Function/displayName\"><code>Function: displayName</code></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/Function/length\"><code>Function: length</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/name\"><code>Function: name</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/prototype\"><code>Function: prototype</code></a></li></ol></details></li><li><details><summary>Instance methods</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__\"><code>Object.prototype.__defineGetter__()</code></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/Object/__defineSetter__\"><code>Object.prototype.__defineSetter__()</code></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/Object/__lookupGetter__\"><code>Object.prototype.__lookupGetter__()</code></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/Object/__lookupSetter__\"><code>Object.prototype.__lookupSetter__()</code></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/Object/hasOwnProperty\"><code>Object.prototype.hasOwnProperty()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf\"><code>Object.prototype.isPrototypeOf()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable\"><code>Object.prototype.propertyIsEnumerable()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString\"><code>Object.prototype.toLocaleString()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString\"><code>Object.prototype.toString()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf\"><code>Object.prototype.valueOf()</code></a></li></ol></details></li><li><details><summary>Instance properties</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor\"><code>Object.prototype.constructor</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto\"><code>Object.prototype.__proto__</code></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></ol>","sidebarMacro":"JSRef","body":[{"type":"prose","value":{"id":null,"title":null,"isH3":false,"content":"<p>The <strong><code>Object</code></strong> type represents one of <a href=\"/en-US/docs/Web/JavaScript/Data_structures\">JavaScript's data types</a>. It is used to store various keyed collections and more complex entities. Objects can be created using the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object\"><code>Object()</code></a> constructor or the <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer\">object initializer / literal syntax</a>.</p>"}},{"type":"prose","value":{"id":"description","title":"Description","isH3":false,"content":"<p>Nearly all <a href=\"/en-US/docs/Web/JavaScript/Data_structures#objects\">objects</a> in JavaScript are instances of <code>Object</code>; a typical object inherits properties (including methods) from <code>Object.prototype</code>, although these properties may be shadowed (a.k.a. overridden). The only objects that don't inherit from <code>Object.prototype</code> are those with <a href=\"#null-prototype_objects\"><code>null</code> prototype</a>, or descended from other <code>null</code> prototype objects.</p>\n<p>Changes to the <code>Object.prototype</code> object are seen by <strong>all</strong> objects through prototype chaining, unless the properties and methods subject to those changes are overridden further along the prototype chain. This provides a very powerful although potentially dangerous mechanism to override or extend object behavior. To make it more secure, <code>Object.prototype</code> is the only object in the core JavaScript language that has <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf#description\">immutable prototype</a> — the prototype of <code>Object.prototype</code> is always <code>null</code> and not changeable.</p>"}},{"type":"prose","value":{"id":"object_prototype_properties","title":"Object prototype properties","isH3":true,"content":"<p>You should avoid calling any <code>Object.prototype</code> method directly from the instance, especially those that are not intended to be polymorphic (i.e. only its initial behavior makes sense and no descending object could override it in a meaningful way). All objects descending from <code>Object.prototype</code> may define a custom own property that has the same name, but with entirely different semantics from what you expect. Furthermore, these properties are not inherited by <a href=\"#null-prototype_objects\"><code>null</code>-prototype objects</a>. All modern JavaScript utilities for working with objects are <a href=\"#static_methods\">static</a>. More specifically:</p>\n<ul>\n <li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf\"><code>valueOf()</code></a>, <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString\"><code>toString()</code></a>, and <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString\"><code>toLocaleString()</code></a> exist to be polymorphic and you should expect the object to define its own implementation with sensible behaviors, so you can call them as instance methods. However, <code>valueOf()</code> and <code>toString()</code> are usually implicitly called through <a href=\"/en-US/docs/Web/JavaScript/Data_structures#type_coercion\">type conversion</a> and you don't need to call them yourself in your code.</li>\n <li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__\"><code>__defineGetter__()</code></a>, <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineSetter__\"><code>__defineSetter__()</code></a>, <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupGetter__\"><code>__lookupGetter__()</code></a>, and <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupSetter__\"><code>__lookupSetter__()</code></a> are deprecated and should not be used. Use the static alternatives <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty\"><code>Object.defineProperty()</code></a> and <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptor\"><code>Object.getOwnPropertyDescriptor()</code></a> instead.</li>\n <li>The <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto\"><code>__proto__</code></a> property is deprecated and should not be used. The <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getPrototypeOf\"><code>Object.getPrototypeOf()</code></a> and <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf\"><code>Object.setPrototypeOf()</code></a> alternatives are static methods.</li>\n <li>The <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable\"><code>propertyIsEnumerable()</code></a> and <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty\"><code>hasOwnProperty()</code></a> methods can be replaced with the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptor\"><code>Object.getOwnPropertyDescriptor()</code></a> and <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwn\"><code>Object.hasOwn()</code></a> static methods, respectively.</li>\n <li>The <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf\"><code>isPrototypeOf()</code></a> method can usually be replaced with <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/instanceof\"><code>instanceof</code></a>, if you are checking the <code>prototype</code> property of a constructor.</li>\n</ul>\n<p>In case where a semantically equivalent static method doesn't exist, or if you really want to use the <code>Object.prototype</code> method, you should directly <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call\"><code>call()</code></a> the <code>Object.prototype</code> method on your target object instead, to prevent the object from having an overriding property that produces unexpected results.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const obj = {\n foo: 1,\n // You should not define such a method on your own object,\n // but you may not be able to prevent it from happening if\n // you are receiving the object from external input\n propertyIsEnumerable() {\n return false;\n },\n};\n\nobj.propertyIsEnumerable(\"foo\"); // false; unexpected result\nObject.prototype.propertyIsEnumerable.call(obj, \"foo\"); // true; expected result\n</code></pre></div>"}},{"type":"prose","value":{"id":"deleting_a_property_from_an_object","title":"Deleting a property from an object","isH3":true,"content":"<p>There isn't any method in an Object itself to delete its own properties (such as <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/delete\"><code>Map.prototype.delete()</code></a>). To do so, one must use the <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/delete\"><code>delete</code></a> operator.</p>"}},{"type":"prose","value":{"id":"null-prototype_objects","title":"null-prototype objects","isH3":true,"content":"<p>Almost all objects in JavaScript ultimately inherit from <code>Object.prototype</code> (see <a href=\"/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain\">inheritance and the prototype chain</a>). However, you may create <code>null</code>-prototype objects using <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create\"><code>Object.create(null)</code></a> or the <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer\">object initializer syntax</a> with <code>__proto__: null</code> (note: the <code>__proto__</code> key in object literals is different from the deprecated <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto\"><code>Object.prototype.__proto__</code></a> property). You can also change the prototype of an existing object to <code>null</code> by calling <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf\"><code>Object.setPrototypeOf(obj, null)</code></a>.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const obj = Object.create(null);\nconst obj2 = { __proto__: null };\n</code></pre></div>\n<p>An object with a <code>null</code> prototype can behave in unexpected ways, because it doesn't inherit any object methods from <code>Object.prototype</code>. This is especially true when debugging, since common object-property converting/detecting utility functions may generate errors, or lose information (especially if using silent error-traps that ignore errors).</p>\n<p>For example, the lack of <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString\"><code>Object.prototype.toString()</code></a> often makes debugging intractable:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const normalObj = {}; // create a normal object\nconst nullProtoObj = Object.create(null); // create an object with \"null\" prototype\n\nconsole.log(`normalObj is: ${normalObj}`); // shows \"normalObj is: [object Object]\"\nconsole.log(`nullProtoObj is: ${nullProtoObj}`); // throws error: Cannot convert object to primitive value\n\nalert(normalObj); // shows [object Object]\nalert(nullProtoObj); // throws error: Cannot convert object to primitive value\n</code></pre></div>\n<p>Other methods will fail as well.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>normalObj.valueOf(); // shows {}\nnullProtoObj.valueOf(); // throws error: nullProtoObj.valueOf is not a function\n\nnormalObj.hasOwnProperty(\"p\"); // shows \"true\"\nnullProtoObj.hasOwnProperty(\"p\"); // throws error: nullProtoObj.hasOwnProperty is not a function\n\nnormalObj.constructor; // shows \"Object() { [native code] }\"\nnullProtoObj.constructor; // shows \"undefined\"\n</code></pre></div>\n<p>We can add the <code>toString</code> method back to the null-prototype object by assigning it one:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>nullProtoObj.toString = Object.prototype.toString; // since new object lacks toString, add the original generic one back\n\nconsole.log(nullProtoObj.toString()); // shows \"[object Object]\"\nconsole.log(`nullProtoObj is: ${nullProtoObj}`); // shows \"nullProtoObj is: [object Object]\"\n</code></pre></div>\n<p>Unlike normal objects, in which <code>toString()</code> is on the object's prototype, the <code>toString()</code> method here is an own property of <code>nullProtoObj</code>. This is because <code>nullProtoObj</code> has no (<code>null</code>) prototype.</p>\n<p>You can also revert a null-prototype object back to an ordinary object using <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf\"><code>Object.setPrototypeOf(nullProtoObj, Object.prototype)</code></a>.</p>\n<p>In practice, objects with <code>null</code> prototype are usually used as a cheap substitute for <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map\">maps</a>. The presence of <code>Object.prototype</code> properties will cause some bugs:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const ages = { alice: 18, bob: 27 };\n\nfunction hasPerson(name) {\n return name in ages;\n}\n\nfunction getAge(name) {\n return ages[name];\n}\n\nhasPerson(\"hasOwnProperty\"); // true\ngetAge(\"toString\"); // [Function: toString]\n</code></pre></div>\n<p>Using a null-prototype object removes this hazard without introducing too much complexity to the <code>hasPerson</code> and <code>getAge</code> functions:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const ages = Object.create(null, {\n alice: { value: 18, enumerable: true },\n bob: { value: 27, enumerable: true },\n});\n\nhasPerson(\"hasOwnProperty\"); // false\ngetAge(\"toString\"); // undefined\n</code></pre></div>\n<p>In such case, the addition of any method should be done cautiously, as they can be confused with the other key-value pairs stored as data.</p>\n<p>Making your object not inherit from <code>Object.prototype</code> also prevents prototype pollution attacks. If a malicious script adds a property to <code>Object.prototype</code>, it will be accessible on every object in your program, except objects that have null prototype.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const user = {};\n\n// A malicious script:\nObject.prototype.authenticated = true;\n\n// Unexpectedly allowing unauthenticated user to pass through\nif (user.authenticated) {\n // access confidential data\n}\n</code></pre></div>\n<p>JavaScript also has built-in APIs that produce <code>null</code>-prototype objects, especially those that use objects as ad hoc key-value collections. For example:</p>\n<ul>\n <li>The return value of <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/groupBy\"><code>Object.groupBy()</code></a></li>\n <li>The <code>groups</code> and <code>indices.groups</code> properties of the result of <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec\"><code>RegExp.prototype.exec()</code></a></li>\n <li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Symbol.unscopables\"><code>Array.prototype[Symbol.unscopables]</code></a> (all <code>[Symbol.unscopables]</code> objects should have <code>null</code>-prototype)</li>\n <li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/import.meta\"><code>import.meta</code></a></li>\n <li>Module namespace objects, obtained through <a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/import#namespace_import\"><code>import * as ns from \"module\";</code></a> or <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/import\"><code>import()</code></a></li>\n</ul>\n<p>The term \"<code>null</code>-prototype object\" often also includes any object without <code>Object.prototype</code> in its prototype chain. Such objects can be created with <a href=\"/en-US/docs/Web/JavaScript/Reference/Classes/extends#extending_null\"><code>extends null</code></a> when using classes.</p>"}},{"type":"prose","value":{"id":"object_coercion","title":"Object coercion","isH3":true,"content":"<p>Many built-in operations that expect objects first coerce their arguments to objects. <a href=\"https://tc39.es/ecma262/multipage/abstract-operations.html#sec-toobject\" class=\"external\" target=\"_blank\">The operation</a> can be summarized as follows:</p>\n<ul>\n <li>Objects are returned as-is.</li>\n <li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined\"><code>undefined</code></a> and <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/null\"><code>null</code></a> throw a <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError\"><code>TypeError</code></a>.</li>\n <li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number\"><code>Number</code></a>, <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/String\"><code>String</code></a>, <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean\"><code>Boolean</code></a>, <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol\"><code>Symbol</code></a>, <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt\"><code>BigInt</code></a> primitives are wrapped into their corresponding object wrappers.</li>\n</ul>\n<p>There are two ways to achieve nearly the same effect in JavaScript.</p>\n<ul>\n <li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf\"><code>Object.prototype.valueOf()</code></a>: <code>Object.prototype.valueOf.call(x)</code> does exactly the object coercion steps explained above to convert <code>x</code>.</li>\n <li>The <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object\"><code>Object()</code></a> function: <code>Object(x)</code> uses the same algorithm to convert <code>x</code>, except that <code>undefined</code> and <code>null</code> don't throw a <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError\"><code>TypeError</code></a>, but return a plain object.</li>\n</ul>\n<p>Places that use object coercion include:</p>\n<ul>\n <li>The <code>object</code> parameter of <a href=\"/en-US/docs/Web/JavaScript/Reference/Statements/for...in\"><code>for...in</code></a> loops.</li>\n <li>The <code>this</code> value of <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array\"><code>Array</code></a> methods.</li>\n <li>Parameters of <code>Object</code> methods such as <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys\"><code>Object.keys()</code></a>.</li>\n <li>Auto-boxing when a property is accessed on a primitive value, since primitives do not have properties.</li>\n <li>The <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/this\"><code>this</code></a> value when calling a non-strict function. Primitives are boxed while <code>null</code> and <code>undefined</code> are replaced with the <a href=\"/en-US/docs/Glossary/Global_object\">global object</a>.</li>\n</ul>\n<p>Unlike <a href=\"/en-US/docs/Web/JavaScript/Data_structures#primitive_coercion\">conversion to primitives</a>, the object coercion process itself is not observable in any way, since it doesn't invoke custom code like <code>toString</code> or <code>valueOf</code> methods.</p>"}},{"type":"prose","value":{"id":"constructor","title":"Constructor","isH3":false,"content":"<dl>\n <dt id=\"object\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object\"><code>Object()</code></a></dt>\n <dd>\n <p>Turns the input into an object.</p>\n </dd>\n</dl>"}},{"type":"prose","value":{"id":"static_methods","title":"Static methods","isH3":false,"content":"<dl>\n <dt id=\"object.assign\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign\"><code>Object.assign()</code></a></dt>\n <dd>\n <p>Copies the values of all enumerable own properties from one or more source objects to a target object.</p>\n </dd>\n <dt id=\"object.create\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create\"><code>Object.create()</code></a></dt>\n <dd>\n <p>Creates a new object with the specified prototype object and properties.</p>\n </dd>\n <dt id=\"object.defineproperties\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties\"><code>Object.defineProperties()</code></a></dt>\n <dd>\n <p>Adds the named properties described by the given descriptors to an object.</p>\n </dd>\n <dt id=\"object.defineproperty\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty\"><code>Object.defineProperty()</code></a></dt>\n <dd>\n <p>Adds the named property described by a given descriptor to an object.</p>\n </dd>\n <dt id=\"object.entries\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries\"><code>Object.entries()</code></a></dt>\n <dd>\n <p>Returns an array containing all of the <code>[key, value]</code> pairs of a given object's <strong>own</strong> enumerable string properties.</p>\n </dd>\n <dt id=\"object.freeze\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze\"><code>Object.freeze()</code></a></dt>\n <dd>\n <p>Freezes an object. Other code cannot delete or change its properties.</p>\n </dd>\n <dt id=\"object.fromentries\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries\"><code>Object.fromEntries()</code></a></dt>\n <dd>\n <p>Returns a new object from an iterable of <code>[key, value]</code> pairs. (This is the reverse of <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries\"><code>Object.entries</code></a>).</p>\n </dd>\n <dt id=\"object.getownpropertydescriptor\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptor\"><code>Object.getOwnPropertyDescriptor()</code></a></dt>\n <dd>\n <p>Returns a property descriptor for a named property on an object.</p>\n </dd>\n <dt id=\"object.getownpropertydescriptors\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptors\"><code>Object.getOwnPropertyDescriptors()</code></a></dt>\n <dd>\n <p>Returns an object containing all own property descriptors for an object.</p>\n </dd>\n <dt id=\"object.getownpropertynames\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames\"><code>Object.getOwnPropertyNames()</code></a></dt>\n <dd>\n <p>Returns an array containing the names of all of the given object's <strong>own</strong> enumerable and non-enumerable properties.</p>\n </dd>\n <dt id=\"object.getownpropertysymbols\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols\"><code>Object.getOwnPropertySymbols()</code></a></dt>\n <dd>\n <p>Returns an array of all symbol properties found directly upon a given object.</p>\n </dd>\n <dt id=\"object.getprototypeof\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getPrototypeOf\"><code>Object.getPrototypeOf()</code></a></dt>\n <dd>\n <p>Returns the prototype (internal <code>[[Prototype]]</code> property) of the specified object.</p>\n </dd>\n <dt id=\"object.groupby\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/groupBy\"><code>Object.groupBy()</code></a></dt>\n <dd>\n <p>Groups the elements of a given iterable according to the string values returned by a provided callback function. The returned object has separate properties for each group, containing arrays with the elements in the group.</p>\n </dd>\n <dt id=\"object.hasown\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwn\"><code>Object.hasOwn()</code></a></dt>\n <dd>\n <p>Returns <code>true</code> if the specified object has the indicated property as its <em>own</em> property, or <code>false</code> if the property is inherited or does not exist.</p>\n </dd>\n <dt id=\"object.is\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is\"><code>Object.is()</code></a></dt>\n <dd>\n <p>Compares if two values are the same value. Equates all <code>NaN</code> values (which differs from both <code>IsLooselyEqual</code> used by <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Equality\"><code>==</code></a> and <code>IsStrictlyEqual</code> used by <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Strict_equality\"><code>===</code></a>).</p>\n </dd>\n <dt id=\"object.isextensible\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isExtensible\"><code>Object.isExtensible()</code></a></dt>\n <dd>\n <p>Determines if extending of an object is allowed.</p>\n </dd>\n <dt id=\"object.isfrozen\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isFrozen\"><code>Object.isFrozen()</code></a></dt>\n <dd>\n <p>Determines if an object was frozen.</p>\n </dd>\n <dt id=\"object.issealed\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isSealed\"><code>Object.isSealed()</code></a></dt>\n <dd>\n <p>Determines if an object is sealed.</p>\n </dd>\n <dt id=\"object.keys\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys\"><code>Object.keys()</code></a></dt>\n <dd>\n <p>Returns an array containing the names of all of the given object's <strong>own</strong> enumerable string properties.</p>\n </dd>\n <dt id=\"object.preventextensions\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/preventExtensions\"><code>Object.preventExtensions()</code></a></dt>\n <dd>\n <p>Prevents any extensions of an object.</p>\n </dd>\n <dt id=\"object.seal\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/seal\"><code>Object.seal()</code></a></dt>\n <dd>\n <p>Prevents other code from deleting properties of an object.</p>\n </dd>\n <dt id=\"object.setprototypeof\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf\"><code>Object.setPrototypeOf()</code></a></dt>\n <dd>\n <p>Sets the object's prototype (its internal <code>[[Prototype]]</code> property).</p>\n </dd>\n <dt id=\"object.values\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/values\"><code>Object.values()</code></a></dt>\n <dd>\n <p>Returns an array containing the values that correspond to all of a given object's <strong>own</strong> enumerable string properties.</p>\n </dd>\n</dl>"}},{"type":"prose","value":{"id":"instance_properties","title":"Instance properties","isH3":false,"content":"<p>These properties are defined on <code>Object.prototype</code> and shared by all <code>Object</code> instances.</p>\n<dl>\n <dt id=\"object.prototype.__proto__\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto\"><code>Object.prototype.__proto__</code></a> <abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></dt>\n <dd>\n <p>Points to the object which was used as prototype when the object was instantiated.</p>\n </dd>\n <dt id=\"object.prototype.constructor\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor\"><code>Object.prototype.constructor</code></a></dt>\n <dd>\n <p>The constructor function that created the instance object. For plain <code>Object</code> instances, the initial value is the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object\"><code>Object</code></a> constructor. Instances of other constructors each inherit the <code>constructor</code> property from their respective <code>Constructor.prototype</code> object.</p>\n </dd>\n</dl>"}},{"type":"prose","value":{"id":"instance_methods","title":"Instance methods","isH3":false,"content":"<dl>\n <dt id=\"object.prototype.__definegetter__\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__\"><code>Object.prototype.__defineGetter__()</code></a> <abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></dt>\n <dd>\n <p>Associates a function with a property that, when accessed, executes that function and returns its return value.</p>\n </dd>\n <dt id=\"object.prototype.__definesetter__\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineSetter__\"><code>Object.prototype.__defineSetter__()</code></a> <abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></dt>\n <dd>\n <p>Associates a function with a property that, when set, executes that function which modifies the property.</p>\n </dd>\n <dt id=\"object.prototype.__lookupgetter__\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupGetter__\"><code>Object.prototype.__lookupGetter__()</code></a> <abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></dt>\n <dd>\n <p>Returns the function bound as a getter to the specified property.</p>\n </dd>\n <dt id=\"object.prototype.__lookupsetter__\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupSetter__\"><code>Object.prototype.__lookupSetter__()</code></a> <abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></dt>\n <dd>\n <p>Returns the function bound as a setter to the specified property.</p>\n </dd>\n <dt id=\"object.prototype.hasownproperty\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty\"><code>Object.prototype.hasOwnProperty()</code></a></dt>\n <dd>\n <p>Returns a boolean indicating whether an object contains the specified property as a direct property of that object and not inherited through the prototype chain.</p>\n </dd>\n <dt id=\"object.prototype.isprototypeof\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf\"><code>Object.prototype.isPrototypeOf()</code></a></dt>\n <dd>\n <p>Returns a boolean indicating whether the object this method is called upon is in the prototype chain of the specified object.</p>\n </dd>\n <dt id=\"object.prototype.propertyisenumerable\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable\"><code>Object.prototype.propertyIsEnumerable()</code></a></dt>\n <dd>\n <p>Returns a boolean indicating whether the specified property is the object's <a href=\"/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_properties\">enumerable own</a> property.</p>\n </dd>\n <dt id=\"object.prototype.tolocalestring\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString\"><code>Object.prototype.toLocaleString()</code></a></dt>\n <dd>\n <p>Calls <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString\"><code>toString()</code></a>.</p>\n </dd>\n <dt id=\"object.prototype.tostring\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString\"><code>Object.prototype.toString()</code></a></dt>\n <dd>\n <p>Returns a string representation of the object.</p>\n </dd>\n <dt id=\"object.prototype.valueof\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf\"><code>Object.prototype.valueOf()</code></a></dt>\n <dd>\n <p>Returns the primitive value of the specified object.</p>\n </dd>\n</dl>"}},{"type":"prose","value":{"id":"examples","title":"Examples","isH3":false,"content":""}},{"type":"prose","value":{"id":"constructing_empty_objects","title":"Constructing empty objects","isH3":true,"content":"<p>The following example creates empty objects using the <code>new</code> keyword with different arguments:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const o1 = new Object();\nconst o2 = new Object(undefined);\nconst o3 = new Object(null);\n</code></pre></div>"}},{"type":"prose","value":{"id":"using_object_constructor_to_turn_primitives_into_an_object_of_their_respective_type","title":"Using Object() constructor to turn primitives into an Object of their respective type","isH3":true,"content":"<p>You can use the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/Object\"><code>Object()</code></a> constructor to create an object wrapper of a primitive value.</p>\n<p>The following examples create variables <code>o1</code> and <code>o2</code> which are objects storing <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean\"><code>Boolean</code></a> and <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt\"><code>BigInt</code></a> values:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// Equivalent to const o1 = new Boolean(true)\nconst o1 = new Object(true);\n\n// No equivalent because BigInt() can't be called as a constructor,\n// and calling it as a regular function won't create an object\nconst o2 = new Object(1n);\n</code></pre></div>"}},{"type":"prose","value":{"id":"object_prototypes","title":"Object prototypes","isH3":true,"content":"<p>When altering the behavior of existing <code>Object.prototype</code> methods, consider injecting code by wrapping your extension before or after the existing logic. For example, this (untested) code will pre-conditionally execute custom logic before the built-in logic or someone else's extension is executed.</p>\n<p>When modifying prototypes with hooks, pass <code>this</code> and the arguments (the call state) to the current behavior by calling <code>apply()</code> on the function. This pattern can be used for any prototype, such as <code>Node.prototype</code>, <code>Function.prototype</code>, etc.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const current = Object.prototype.valueOf;\n\n// Since my property \"-prop-value\" is cross-cutting and isn't always\n// on the same prototype chain, I want to modify Object.prototype:\nObject.prototype.valueOf = function (...args) {\n if (Object.hasOwn(this, \"-prop-value\")) {\n return this[\"-prop-value\"];\n } else {\n // It doesn't look like one of my objects, so let's fall back on\n // the default behavior by reproducing the current behavior as best we can.\n // The apply behaves like \"super\" in some other languages.\n // Even though valueOf() doesn't take arguments, some other hook may.\n return current.apply(this, args);\n }\n};\n</code></pre></div>\n<div class=\"notecard warning\">\n <p><strong>Warning:</strong> Modifying the <code>prototype</code> property of any built-in constructor is considered a bad practice and risks forward compatibility.</p>\n</div>\n<p>You can read more about prototypes in <a href=\"/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain\">Inheritance and the prototype chain</a>.</p>"}},{"type":"specifications","value":{"title":"Specifications","id":"specifications","isH3":false,"specifications":[{"bcdSpecificationURL":"https://tc39.es/ecma262/multipage/fundamental-objects.html#sec-object-objects","title":"ECMAScript Language Specification"}],"query":"javascript.builtins.Object"}},{"type":"browser_compatibility","value":{"title":"Browser compatibility","id":"browser_compatibility","isH3":false,"query":"javascript.builtins.Object"}},{"type":"prose","value":{"id":"see_also","title":"See also","isH3":false,"content":"<ul>\n <li><a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer\">Object initializer</a></li>\n</ul>"}}],"toc":[{"text":"Description","id":"description"},{"text":"Constructor","id":"constructor"},{"text":"Static methods","id":"static_methods"},{"text":"Instance properties","id":"instance_properties"},{"text":"Instance methods","id":"instance_methods"},{"text":"Examples","id":"examples"},{"text":"Specifications","id":"specifications"},{"text":"Browser compatibility","id":"browser_compatibility"},{"text":"See also","id":"see_also"}],"summary":"The Object type represents one of JavaScript's data types. It is used to store various keyed collections and more complex entities. Objects can be created using the Object() constructor or the object initializer / literal syntax.","popularity":0.1678,"modified":"2024-07-25T21:32:46.000Z","other_translations":[{"locale":"de","title":"Object","native":"Deutsch"},{"locale":"es","title":"Object","native":"Español"},{"locale":"fr","title":"Object","native":"Français"},{"locale":"ja","title":"Object","native":"日本語"},{"locale":"ko","title":"Object","native":"한국어"},{"locale":"pt-BR","title":"Object","native":"Português (do Brasil)"},{"locale":"ru","title":"Object","native":"Русский"},{"locale":"zh-CN","title":"Object","native":"中文 (简体)"}],"pageType":"javascript-class","source":{"folder":"en-us/web/javascript/reference/global_objects/object","github_url":"https://github.com/mdn/content/blob/main/files/en-us/web/javascript/reference/global_objects/object/index.md","last_commit_url":"https://github.com/mdn/content/commit/8421c0cd94fa5aa237c833ac6d24885edbc7d721","filename":"index.md"},"short_title":"Object","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/Global_Objects","title":"Standard built-in objects"},{"uri":"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object","title":"Object"}],"pageTitle":"Object - JavaScript | MDN","noIndexing":false}}</script> <script>function gtElInit() {var lib = new google.translate.TranslateService();lib.translatePage('pl', 'tr', function () {});}</script> <script src="https://translate.google.com/translate_a/element.js?cb=gtElInit&hl=en-GB&client=wt" type="text/javascript"></script> </body> </html>