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class=\"sitenotice\" lang=\"en\" dir=\"ltr\"\u003E\u003Ccenter\u003E\n\u003Cdiv style=\"width:100%; padding:15px; border-style:solid; border-width:2px; border-color:var(--color-placeholder, black); font-size:14px; text-align:center;\" class=\"plainlinks\"\u003E\u003Cdiv style=\"vertical-align:middle;margin-top:0.5em\"\u003E\u003Cfigure class=\"mw-halign-left skin-invert\" typeof=\"mw:File\"\u003E\u003Ca href=\"/wiki/MediaWiki_Users_and_Developers_Conference\" title=\"MediaWiki Users and Developers Conference\"\u003E\u003Cimg src=\"//upload.wikimedia.org/wikipedia/commons/thumb/7/71/MediaWikiUsersDevelopersConferenceWordmark.png/120px-MediaWikiUsersDevelopersConferenceWordmark.png\" decoding=\"async\" width=\"100\" height=\"44\" class=\"mw-file-element\" srcset=\"//upload.wikimedia.org/wikipedia/commons/thumb/7/71/MediaWikiUsersDevelopersConferenceWordmark.png/250px-MediaWikiUsersDevelopersConferenceWordmark.png 1.5x\" data-file-width=\"1080\" data-file-height=\"480\" /\u003E\u003C/a\u003E\u003Cfigcaption\u003E\u003C/figcaption\u003E\u003C/figure\u003E\u003C/div\u003E\n\u003Cp\u003EEarly bird tickets for the \u003Ca href=\"/wiki/MediaWiki_Users_and_Developers_Workshop_Spring_2025\" title=\"MediaWiki Users and Developers Workshop Spring 2025\"\u003EMediaWiki Users and Developers Workshop Spring 2025\u003C/a\u003E in \u003Ca href=\"https://en.wikipedia.org/wiki/Sandusky,_Ohio\" class=\"extiw\" title=\"w:Sandusky, Ohio\"\u003ESandusky\u003C/a\u003E, Ohio, USA are now \u003Ca rel=\"nofollow\" class=\"external text\" href=\"https://www.eventbrite.com/e/mediawiki-users-and-developers-conference-spring-2025-tickets-1254864847539\"\u003E\u003Cb\u003Eon sale on Eventbrite\u003C/b\u003E\u003C/a\u003E until April 13! In addition, the \u003Ca href=\"/wiki/MediaWiki_Users_and_Developers_Conference/Scholarships\" title=\"MediaWiki Users and Developers Conference/Scholarships\"\u003Escholarship application\u003C/a\u003E is open now until April 15.\n\u003C/p\u003E\n\u003C/div\u003E\n\u003C/center\u003E\u003C/div\u003E\u003C/div\u003E\u003C/div\u003E\u003C/div\u003E";}}());</script></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> <div class="vector-sticky-pinned-container"> <nav id="mw-panel-toc" aria-label="Contents" data-event-name="ui.sidebar-toc" class="mw-table-of-contents-container vector-toc-landmark"> <div id="vector-toc-pinned-container" class="vector-pinned-container"> <div id="vector-toc" class="vector-toc vector-pinnable-element"> <div class="vector-pinnable-header vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">Contents</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">Beginning</div> </a> </li> <li id="toc-Features" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Features"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Features</span> </div> </a> <button aria-controls="toc-Features-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Features subsection</span> </button> <ul id="toc-Features-sublist" class="vector-toc-list"> <li id="toc-Inheritance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Inheritance"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>Inheritance<span> </span></span> </div> </a> <ul id="toc-Inheritance-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Events" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Events"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.2</span> <span>Events<span> </span></span> </div> </a> <ul id="toc-Events-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Registries_and_Factories" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Registries_and_Factories"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.3</span> <span>Registries and Factories<span> </span></span> </div> </a> <ul id="toc-Registries_and_Factories-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Utilities" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Utilities"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.4</span> <span>Utilities</span> </div> </a> <ul id="toc-Utilities-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Compatibility" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Compatibility"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Compatibility</span> </div> </a> <button aria-controls="toc-Compatibility-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Compatibility subsection</span> </button> <ul id="toc-Compatibility-sublist" class="vector-toc-list"> <li id="toc-Extending_OOjs_classes_in_newer_versions_of_ECMAScript" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Extending_OOjs_classes_in_newer_versions_of_ECMAScript"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Extending OOjs classes in newer versions of ECMAScript</span> </div> </a> <ul id="toc-Extending_OOjs_classes_in_newer_versions_of_ECMAScript-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Namespace" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Namespace"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Namespace</span> </div> </a> <ul id="toc-Namespace-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">OOjs</span></h1> <div class="mw-indicators"> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/OOjs" title="View the content page [c]" accesskey="c"><span>Page</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/Talk:OOjs" rel="discussion" title="Discussion about the content page [t]" accesskey="t"><span>Discussion</span></a></li> </ul> </div> </div> <div id="vector-variants-dropdown" class="vector-dropdown emptyPortlet" > <input type="checkbox" id="vector-variants-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-variants-dropdown" class="vector-dropdown-checkbox " aria-label="Change language variant" > <label 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source code of this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-history" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=OOjs&action=history" title="Past revisions of this page [h]" accesskey="h"><span>View history</span></a></li> </ul> </div> </div> </nav> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-dropdown" class="vector-dropdown vector-page-tools-dropdown" > <input type="checkbox" id="vector-page-tools-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-tools-dropdown" class="vector-dropdown-checkbox " aria-label="Tools" > <label id="vector-page-tools-dropdown-label" for="vector-page-tools-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">Tools</span> </label> <div class="vector-dropdown-content"> <div 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here</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Special:RecentChangesLinked/OOjs" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k"><span>Related changes</span></a></li><li id="t-upload" class="mw-list-item"><a href="//commons.wikimedia.org/wiki/Special:UploadWizard" title="Upload files [u]" accesskey="u"><span>Upload file</span></a></li><li id="t-permalink" class="mw-list-item"><a href="/w/index.php?title=OOjs&oldid=6947125" title="Permanent link to this revision of this page"><span>Permanent link</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=OOjs&action=info" title="More information about this page"><span>Page information</span></a></li><li id="t-cite" class="mw-list-item"><a href="/w/index.php?title=Special:CiteThisPage&page=OOjs&id=6947125&wpFormIdentifier=titleform" title="Information on how to cite this page"><span>Cite this page</span></a></li><li id="t-urlshortener" 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href="/w/index.php?title=OOjs&printable=yes" title="Printable version of this page [p]" accesskey="p"><span>Printable version</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects emptyPortlet" > <div class="vector-menu-heading"> In other projects </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header 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id="mw-content-text" class="mw-body-content"><div class="mw-pt-translate-header noprint nomobile" dir="ltr" lang="en"><a href="/w/index.php?title=Special:Translate&group=page-OOjs&action=page&filter=&action_source=translate_page" title="Special:Translate">Translate this page</a></div><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="mw-pt-languages noprint navigation-not-searchable" lang="en" dir="ltr"><div class="mw-pt-languages-label">Languages:</div><ul class="mw-pt-languages-list"><li><a href="/w/index.php?title=Special:Translate&group=page-OOjs&language=&task=view" class="new" title="Start translation for this language" lang="" dir="ltr"></a></li> <li><a href="/wiki/OOjs/de" class="mw-pt-progress mw-pt-progress--med" title="OOjs (19% translated)" lang="de" dir="ltr">Deutsch</a></li> <li><span class="mw-pt-languages-ui mw-pt-languages-selected mw-pt-progress mw-pt-progress--complete" lang="en" dir="ltr">English</span></li> <li><a href="/wiki/OOjs/dag" class="mw-pt-progress mw-pt-progress--low" title="OOjs/dag (3% translated)" lang="dag" dir="ltr">dagbanli</a></li> <li><a href="/wiki/OOjs/fr" class="mw-pt-progress mw-pt-progress--high" title="OOjs (78% translated)" lang="fr" dir="ltr">français</a></li> <li><a href="/wiki/OOjs/hu" class="mw-pt-progress mw-pt-progress--med" title="OOjs (33% translated)" lang="hu" dir="ltr">magyar</a></li> <li><a href="/wiki/OOjs/pl" class="mw-pt-progress mw-pt-progress--med" title="OOjs (17% translated)" lang="pl" dir="ltr">polski</a></li> <li><a href="/wiki/OOjs/ru" class="mw-pt-progress mw-pt-progress--low" title="OOjs (8% translated)" lang="ru" dir="ltr">русский</a></li> <li><a href="/wiki/OOjs/gu" class="mw-pt-progress mw-pt-progress--low" title="OOjs/gu (3% translated)" lang="gu" dir="ltr">ગુજરાતી</a></li> <li><a href="/wiki/OOjs/ja" class="mw-pt-progress mw-pt-progress--med" title="OOjs (31% translated)" lang="ja" dir="ltr">日本語</a></li> <li><a href="/wiki/OOjs/nan" class="mw-pt-progress mw-pt-progress--med" title="OOjs (28% translated)" lang="nan" dir="ltr">閩南語 / Bân-lâm-gú</a></li></ul></div> <style data-mw-deduplicate="TemplateStyles:r6605224">.mw-parser-output .tpl-sidebar{background-color:var(--background-color-interactive-subtle,#f8f9fa);border:1px solid var(--border-color-divider,#a2a9b1);color:var(--color-base,#202122);width:22em;padding:.2em;text-align:center;line-height:1.4em;font-size:88%}.mw-parser-output .tpl-sidebar-pagedir-ltr,.mw-parser-output .tpl-sidebar.tpl-sidebar-floatright{float:right;clear:right;margin:.5em 0 1em 1em}.mw-parser-output .tpl-sidebar-pagedir-rtl,.mw-parser-output .tpl-sidebar.tpl-sidebar-floatleft{float:left;clear:left;margin:.5em 1em 1em 0}.mw-parser-output .tpl-sidebar.tpl-sidebar-floatnone{float:none;clear:both;margin:.5em 0 1em 1em}.mw-parser-output .tpl-sidebar>caption{padding-bottom:.2em;font-size:125%;line-height:1.2em;font-weight:bold}.mw-parser-output .tpl-sidebar>tbody>tr>th,.mw-parser-output .tpl-sidebar>tbody>tr>td{padding:0}.mw-parser-output .tpl-sidebar .tpl-sidebar-topimage>td{padding:.4em 0}.mw-parser-output .tpl-sidebar-imagecaption{padding-top:.2em;line-height:1.2em}.mw-parser-output .tpl-sidebar .tpl-sidebar-pretitle>td{padding-top:.4em;line-height:1.2em}.mw-parser-output .tpl-sidebar .tpl-sidebar-topimage+.tpl-sidebar-pretitle>td{padding-top:.2em}.mw-parser-output .tpl-sidebar .tpl-sidebar-title>th{padding:.2em .4em .2em;font-size:145%;line-height:1.2em}.mw-parser-output .tpl-sidebar .tpl-sidebar-pretitle+.tpl-sidebar-title>th{padding-top:0}.mw-parser-output .tpl-sidebar .tpl-sidebar-image>td{padding:.2em 0 .4em}.mw-parser-output .tpl-sidebar .tpl-sidebar-abovebelow>td{padding:.3em .4em;font-weight:bold}.mw-parser-output .tpl-sidebar .tpl-sidebar-heading>th{padding-top:.2em}.mw-parser-output .tpl-sidebar .tpl-sidebar-image~.tpl-sidebar-heading-first>th{padding-top:.4em}.mw-parser-output .tpl-sidebar .tpl-sidebar-content>td{padding-bottom:.2em}.mw-parser-output .tpl-sidebar :not(.tpl-sidebar-heading)+.tpl-sidebar-content-first>td{padding-top:.2em}.mw-parser-output .tpl-sidebar-navbar>td{font-size:115%}.mw-parser-output .tpl-sidebar-pagedir-ltr .tpl-sidebar-navbar>td{text-align:right}.mw-parser-output .tpl-sidebar-pagedir-rtl .tpl-sidebar-navbar>td{text-align:left}</style><table class="vertical-navbox tpl-sidebar tpl-sidebar-pagedir-ltr nowraplinks" role="navigation" style="width:22em; border-spacing: 0.4em 0;"><tbody><tr class="tpl-sidebar-title"> <th class="" style=""><b><a href="/wiki/Special:MyLanguage/OOjs" title="Special:MyLanguage/OOjs">OOjs</a></b><span style="display:none"><a class="mw-selflink selflink"> </a></span></th> </tr><tr class="tpl-sidebar-heading tpl-sidebar-heading-first"> <th class="" style="font-size:130%;">Features</th> </tr><tr class="tpl-sidebar-content tpl-sidebar-content-first"> <td class="" style="text-align:left;"> <ul><li><a href="/wiki/Special:MyLanguage/OOjs/Inheritance" title="Special:MyLanguage/OOjs/Inheritance">Inheritance</a><span style="display:none"><a href="/wiki/OOjs/Inheritance" title="OOjs/Inheritance"> </a></span></li> <li><a href="/wiki/Special:MyLanguage/OOjs/Events" title="Special:MyLanguage/OOjs/Events">Events</a><span style="display:none"><a href="/wiki/OOjs/Events" title="OOjs/Events"> </a></span></li> <li><a href="/wiki/Special:MyLanguage/OOjs/Registries_and_factories" title="Special:MyLanguage/OOjs/Registries and factories">Registries and factories</a><span style="display:none"><a href="/wiki/OOjs/Registries_and_factories" title="OOjs/Registries and factories"> </a></span></li></ul></td> </tr><tr class="tpl-sidebar-heading"> <th class="" style="font-size:130%;">See also</th> </tr><tr class="tpl-sidebar-content"> <td class="" style="text-align:left;"> <ul><li><a href="/wiki/Special:MyLanguage/OOUI" title="Special:MyLanguage/OOUI">OOUI</a><span style="display:none"><a href="/wiki/OOUI" title="OOUI"> </a></span></li></ul></td> </tr><tr class="tpl-sidebar-navbar"> <td style=""><style data-mw-deduplicate="TemplateStyles:r4692751">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar ul{display:inline;white-space:nowrap}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em;width:6em}</style><span class="noprint plainlinks navbar" style=""><small><span style="white-space:nowrap;word-spacing:-.12em;"><a href="/wiki/Template:OOjs_sidebar" title="Template:OOjs sidebar"><span style="" title="View this template">v</span></a><span style=""> <b>·</b> </span><a class="external text" href="https://www.mediawiki.org/wiki/Template_talk:OOjs_sidebar"><span style="" title="Discuss this template">d</span></a><span style=""> <b>·</b> </span><a class="external text" href="https://www.mediawiki.org/w/index.php?title=Template:OOjs_sidebar&action=edit"><span style="" title="Edit this template">e</span></a></span></small></span></td> </tr> </tbody></table> <p><b>OOjs</b> (short for "Object-oriented JavaScript") is a JavaScript library for working with objects. Features include <a href="/wiki/Special:MyLanguage/OOjs/Inheritance#Classes" title="Special:MyLanguage/OOjs/Inheritance">inheritance</a><span style="display:none"><a href="/wiki/OOjs/Inheritance#Classes" title="OOjs/Inheritance"> </a></span>, <a href="/wiki/Special:MyLanguage/OOjs/Inheritance#Mixins" title="Special:MyLanguage/OOjs/Inheritance">mixins</a><span style="display:none"><a href="/wiki/OOjs/Inheritance#Mixins" title="OOjs/Inheritance"> </a></span>, <a href="/wiki/Special:MyLanguage/OOjs/Inheritance#Static_methods_and_properties" title="Special:MyLanguage/OOjs/Inheritance">static inheritance</a><span style="display:none"><a href="/wiki/OOjs/Inheritance#Static_methods_and_properties" title="OOjs/Inheritance"> </a></span> and additional utilities for working with objects and arrays. It also provides an <a href="/wiki/Special:MyLanguage/OOjs/Events" title="Special:MyLanguage/OOjs/Events">EventEmitter</a> mixin for event-driven programming, and a <a href="/wiki/Special:MyLanguage/OOjs/Registries_and_factories" title="Special:MyLanguage/OOjs/Registries and factories">factory</a> pattern for decoupling consumers of functionality from any particular class's implementation. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Features" data-mw-thread-id="h-Features"><span data-mw-comment-start="" id="h-Features"></span>Features<span data-mw-comment-end="h-Features"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=OOjs&action=edit&section=1" title="Edit section: Features"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Inheritance" data-mw-thread-id="h-Inheritance-Features"><span data-mw-comment-start="" id="h-Inheritance-Features"></span><a href="/wiki/Special:MyLanguage/OOjs/Inheritance" title="Special:MyLanguage/OOjs/Inheritance">Inheritance</a><span style="display:none"><a href="/wiki/OOjs/Inheritance" title="OOjs/Inheritance"> </a></span><span data-mw-comment-end="h-Inheritance-Features"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=OOjs&action=edit&section=2" title="Edit section: Inheritance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><code><a href="https://doc.wikimedia.org/oojs/master/OO.html#.inheritClass" class="extiw" title="wmdoc:oojs/master/OO.html">OO.inheritClass( childClass, parentClass )</a></code> </p><p>Extend prototype and static methods and properties of child constructor from a parent constructor. </p><p><code><a href="https://doc.wikimedia.org/oojs/master/OO.html#.mixinClass" class="extiw" title="wmdoc:oojs/master/OO.html">OO.mixinClass( childClass, parentClass )</a></code> </p><p>Copy prototype and static methods and properties to a child constructor from a parent constructor. </p><p><code><a href="https://doc.wikimedia.org/oojs/master/OO.html#.initClass" class="extiw" title="wmdoc:oojs/master/OO.html">OO.initClass( baseClass )</a></code> </p><p>Initialise a base class to be inherited by, or mixed into, a child class. Only required for classes that do not inherit or mixin other classes. </p> <div class="mw-heading mw-heading3"><h3 id="Events" data-mw-thread-id="h-Events-Features"><span data-mw-comment-start="" id="h-Events-Features"></span><a href="/wiki/Special:MyLanguage/OOjs/Events" title="Special:MyLanguage/OOjs/Events">Events</a><span style="display:none"><a href="/wiki/OOjs/Events" title="OOjs/Events"> </a></span><span data-mw-comment-end="h-Events-Features"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=OOjs&action=edit&section=3" title="Edit section: Events"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><code><a href="https://doc.wikimedia.org/oojs/master/#!/api/OO.EventEmitter" class="extiw" title="wmdoc:oojs/master/">OO.EventEmitter</a></code> </p><p>Allow event handlers to be attached, called when events occur, and detached. </p> <div class="mw-heading mw-heading3"><h3 id="Registries_and_Factories" data-mw-thread-id="h-Registries_and_Factories-Features"><span data-mw-comment-start="" id="h-Registries_and_Factories-Features"></span><a href="/wiki/Special:MyLanguage/OOjs/Registries_and_factories" title="Special:MyLanguage/OOjs/Registries and factories">Registries and Factories</a><span style="display:none"><a href="/wiki/OOjs/Registries_and_factories" title="OOjs/Registries and factories"> </a></span><span data-mw-comment-end="h-Registries_and_Factories-Features"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=OOjs&action=edit&section=4" title="Edit section: Registries and Factories"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><code><a href="https://doc.wikimedia.org/oojs/master/#!/api/OO.Registry" class="extiw" title="wmdoc:oojs/master/">OO.Registry</a></code> </p><p>Provide a simple map interface for associating arbitrary data with a symbolic name. </p><p><code><a href="https://doc.wikimedia.org/oojs/master/#!/api/OO.Factory" class="extiw" title="wmdoc:oojs/master/">OO.Factory</a></code> </p><p>Registry of classes with instantiation abstraction. </p> <div class="mw-heading mw-heading3"><h3 id="Utilities" data-mw-thread-id="h-Utilities-Features"><span data-mw-comment-start="" id="h-Utilities-Features"></span>Utilities<span data-mw-comment-end="h-Utilities-Features"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=OOjs&action=edit&section=5" title="Edit section: Utilities"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>See the <a href="https://doc.wikimedia.org/oojs/master/#!/api/OO" class="extiw" title="wmdoc:oojs/master/">API documentation</a> for a complete reference of available utilities. </p> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Compatibility" data-mw-thread-id="h-Compatibility"><span data-mw-comment-start="" id="h-Compatibility"></span>Compatibility<span data-mw-comment-end="h-Compatibility"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=OOjs&action=edit&section=6" title="Edit section: Compatibility"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>OOjs is optimised for modern <b>ECMAScript 5</b> environments. The source code is compatible with the older ECMAScript 3 engine (such as in older versions of Internet Explorer, broadly speaking IE8 and before), but users need a polyfill to provide required ECMAScript 5 methods. </p><p>It is packaged to be run in either Web browsers or Node.js. </p> <div class="mw-heading mw-heading3"><h3 id="Extending_OOjs_classes_in_newer_versions_of_ECMAScript" data-mw-thread-id="h-Extending_OOjs_classes_in_newer_versions_of_ECMAScript-Compatibility"><span data-mw-comment-start="" id="h-Extending_OOjs_classes_in_newer_versions_of_ECMAScript-Compatibility"></span>Extending OOjs classes in newer versions of ECMAScript<span data-mw-comment-end="h-Extending_OOjs_classes_in_newer_versions_of_ECMAScript-Compatibility"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=OOjs&action=edit&section=7" title="Edit section: Extending OOjs classes in newer versions of ECMAScript"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>MediaWiki's ResourceLoader <a href="/wiki/Special:MyLanguage/ResourceLoader/ES6" title="Special:MyLanguage/ResourceLoader/ES6">treats</a><span style="display:none"><a href="/wiki/ResourceLoader/ES6" title="ResourceLoader/ES6"> </a></span> JavaScript code as ES6 by default since MediaWiki 1.41. ES6 supports the <a rel="nofollow" class="external text" href="https://developer.mozilla.org/docs/Web/JavaScript/Reference/Classes"><code>class</code> syntax</a>, so you may declare your extensions of OOjs (and <a href="/wiki/Special:MyLanguage/OOUI" title="Special:MyLanguage/OOUI">OOUI</a><span style="display:none"><a href="/wiki/OOUI" title="OOUI"> </a></span>) classes using the new syntax. For example: </p> <div class="mw-highlight mw-highlight-lang-js mw-content-ltr" dir="ltr"><pre><span></span><span class="kd">class</span><span class="w"> </span><span class="nx">MyDialog</span><span class="w"> </span><span class="k">extends</span><span class="w"> </span><span class="nx">OO</span><span class="p">.</span><span class="nx">ui</span><span class="p">.</span><span class="nx">MessageDialog</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="k">static</span><span class="w"> </span><span class="nx">get</span><span class="w"> </span><span class="nx">name</span><span class="p">()</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="s1">'myDialog'</span><span class="p">;</span> <span class="w"> </span><span class="p">}</span> <span class="w"> </span><span class="kr">constructor</span><span class="p">(</span><span class="nx">config</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="k">super</span><span class="p">(</span><span class="nx">config</span><span class="p">);</span> <span class="w"> </span><span class="c1">// ...</span> <span class="w"> </span><span class="p">}</span> <span class="w"> </span><span class="nx">initialize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="k">super</span><span class="p">.</span><span class="nx">initialize</span><span class="p">();</span> <span class="w"> </span><span class="c1">// ...</span> <span class="w"> </span><span class="p">}</span> <span class="p">}</span> </pre></div> <p>However, you will then need to pass such a class through a helper function like this one: </p> <div class="mw-highlight mw-highlight-lang-js mw-content-ltr" dir="ltr"><pre><span></span><span class="kd">function</span><span class="w"> </span><span class="nx">es6ClassToOoJsClass</span><span class="p">(</span><span class="nx">targetClass</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="kd">const</span><span class="w"> </span><span class="nx">originClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">Object</span><span class="p">.</span><span class="nx">getPrototypeOf</span><span class="p">(</span><span class="nx">targetClass</span><span class="p">);</span> <span class="w"> </span><span class="nx">OO</span><span class="p">.</span><span class="nx">initClass</span><span class="p">(</span><span class="nx">originClass</span><span class="p">);</span> <span class="w"> </span><span class="nx">targetClass</span><span class="p">.</span><span class="k">static</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">Object</span><span class="p">.</span><span class="nx">create</span><span class="p">(</span><span class="nx">originClass</span><span class="p">.</span><span class="k">static</span><span class="p">);</span> <span class="w"> </span><span class="nb">Object</span><span class="p">.</span><span class="nx">getOwnPropertyNames</span><span class="p">(</span><span class="nx">targetClass</span><span class="p">)</span> <span class="w"> </span><span class="p">.</span><span class="nx">filter</span><span class="p">((</span><span class="nx">key</span><span class="p">)</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="nx">key</span><span class="w"> </span><span class="o">!==</span><span class="w"> </span><span class="s1">'static'</span><span class="p">)</span> <span class="w"> </span><span class="p">.</span><span class="nx">forEach</span><span class="p">((</span><span class="nx">key</span><span class="p">)</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="kd">const</span><span class="w"> </span><span class="nx">descriptor</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">Object</span><span class="p">.</span><span class="nx">getOwnPropertyDescriptor</span><span class="p">(</span><span class="nx">targetClass</span><span class="p">,</span><span class="w"> </span><span class="nx">key</span><span class="p">);</span> <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nx">descriptor</span><span class="p">.</span><span class="nx">enumerable</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="nx">descriptor</span><span class="p">.</span><span class="nx">get</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="nx">targetClass</span><span class="p">.</span><span class="k">static</span><span class="p">[</span><span class="nx">key</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">targetClass</span><span class="p">[</span><span class="nx">key</span><span class="p">];</span> <span class="w"> </span><span class="p">}</span> <span class="w"> </span><span class="p">});</span> <span class="w"> </span><span class="nx">targetClass</span><span class="p">.</span><span class="nx">parent</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">targetClass</span><span class="p">.</span><span class="k">super</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">originClass</span><span class="p">;</span> <span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="nx">targetClass</span><span class="p">;</span> <span class="p">}</span> </pre></div> <p>It assumes that the class has no static properties with a getter whose output is not fixed (which is unlikely). </p><p>If you're building your JavaScript project with a transpiler like Babel, you can also use the most modern syntax, with static properties declared as such: </p> <div class="mw-highlight mw-highlight-lang-js mw-content-ltr" dir="ltr"><pre><span></span><span class="w"> </span><span class="k">static</span><span class="w"> </span><span class="nx">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">'myDialog'</span><span class="p">;</span> </pre></div> <p><br /> </p> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Namespace" data-mw-thread-id="h-Namespace"><span data-mw-comment-start="" id="h-Namespace"></span>Namespace<span data-mw-comment-end="h-Namespace"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=OOjs&action=edit&section=8" title="Edit section: Namespace"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In the presence of a module system, such as in Node.js, OOjs exports all of its classes and methods. In other environments, such as Web browsers, a global variable is created named <code>OO</code>. You may access <code>OO</code> the same way you would access <code>jQuery</code> or <code>mediaWiki</code>. </p><p>If you are using eslint, you should add the following to your <code>.eslintrc.json</code> file. </p> <div class="mw-highlight mw-highlight-lang-javascript mw-content-ltr" dir="ltr"><pre><span></span><span class="s2">"globals"</span><span class="o">:</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="s2">"OO"</span><span class="o">:</span><span class="w"> </span><span class="s2">"readonly"</span> <span class="p">}</span> </pre></div> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="See_also" data-mw-thread-id="h-See_also"><span data-mw-comment-start="" id="h-See_also"></span>See also<span data-mw-comment-end="h-See_also"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=OOjs&action=edit&section=9" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r6651102">.mw-parser-output .infobox{box-sizing:border-box;border:2px solid var(--border-color-base,#a2a9b1);width:280px;border-collapse:collapse;border-spacing:0;background-color:white;color:#333;clear:right;float:right;margin:0 0 0.5em 0.5em}.mw-parser-output .infobox-rtl{clear:left;float:left;margin:0 0.5em 0.5em 0}.mw-parser-output .infobox th{text-align:left;padding:0.2em 0.5em;vertical-align:top}.mw-parser-output .infobox-rtl th{text-align:right}@media(max-width:719px){body.mediawiki .mw-parser-output .infobox{float:none;clear:both;width:100%;margin:0 0 .5em 0}}.mw-parser-output .infobox td{border:none;padding:0.2em 0.5em;vertical-align:top}.mw-parser-output .infobox-header{background-color:#a2a9b1;color:#FFF;text-align:left}.mw-parser-output .infobox-header a{color:#FFF}.mw-parser-output .infobox-header td,.mw-parser-output .infobox-header th{padding:0.5em 0.5em}.mw-parser-output .infobox-header img{padding:0 0.2em 0 0.5em}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox{background-color:inherit;color:inherit}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox{background-color:inherit;color:inherit}}</style><style data-mw-deduplicate="TemplateStyles:r7037963">.mw-parser-output .wmf-engineering-project-box{border:1px solid var(--border-color-subtle,#c8ccd1);padding:.2em;width:300px;background:var(--background-color-neutral-subtle,#f8f9fa);color:var(--color-base,#202122)}.mw-parser-output .wmf-engineering-project-box-catlink{font-size:smaller;margin:.2em;text-align:center}.mw-parser-output .wmf-engineering-project-box-title{font-size:1.2em;margin:.2em;background:#14866d;color:#fff;padding:.5em;text-align:center;font-weight:bold}.mw-parser-output .wmf-engineering-project-box-description{margin:.2em;padding:.2em;font-style:italic}.mw-parser-output .wmf-engineering-project-box-data{font-size:.9em;margin:.2em 0;width:100%}.mw-parser-output .wmf-engineering-project-box-data th{width:25%;font-weight:normal}.mw-parser-output .wmf-engineering-project-box-previous,.mw-parser-output .wmf-engineering-project-box-next{font-size:smaller;margin:.2em}.mw-parser-output .infobox-ltr .wmf-engineering-project-box-previous,.mw-parser-output .infobox-rtl .wmf-engineering-project-box-next{float:left}.mw-parser-output .infobox-ltr .wmf-engineering-project-box-next,.mw-parser-output .infobox-rtl .wmf-engineering-project-box-previous{float:right}</style> <table class="infobox infobox-ltr wmf-engineering-project-box plainlinks"><tbody><tr><td> <div class="nomobile wmf-engineering-project-box-catlink"><a href="/wiki/Special:MyLanguage/Category:WMF_Projects" title="Special:MyLanguage/Category:WMF Projects">Wikimedia Foundation projects</a><span style="display:none"><a href="/wiki/Category:WMF_Projects" title="Category:WMF Projects"> </a></span></div> <div class="wmf-engineering-project-box-title">OOjs</div> <div class="wmf-engineering-project-box-description"></div> <table class="wmf-engineering-project-box-data"> <tbody><tr> <th scope="row">Group:</th> <td><a href="/wiki/Editing_team" title="Editing team">Editing team</a></td> </tr> <tr> <th scope="row">Start:</th> <td>2013-10</td> </tr> <tr> <th scope="row">Lead:</th> <td><a href="/wiki/User:Krinkle" title="User:Krinkle">Timo Tijhof</a></td> </tr> <tr class="mw-empty-elt"> </tr></tbody></table></td></tr></tbody></table> <ul><li><a href="/wiki/Special:MyLanguage/OOUI" title="Special:MyLanguage/OOUI">OOUI</a><span style="display:none"><a href="/wiki/OOUI" title="OOUI"> </a></span></li></ul> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="External_links" data-mw-thread-id="h-External_links"><span data-mw-comment-start="" id="h-External_links"></span>External links<span data-mw-comment-end="h-External_links"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=OOjs&action=edit&section=10" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a class="external text" href="https://phabricator.wikimedia.org/diffusion/GOJS/browse/">Source code on phabricator.wikimedia.org/diffusion/</a> (<a rel="nofollow" class="external text" href="https://github.com/wikimedia/oojs">GitHub mirror</a>)</li> <li><a rel="nofollow" class="external text" href="https://npmjs.org/package/oojs">Package on npmjs.org</a></li> <li><a href="https://phabricator.wikimedia.org/tag/oojs" class="extiw" title="phab:tag/oojs">Phabricator project (issue tracker)</a></li> <li><a href="https://doc.wikimedia.org/VisualEditor/master/#!/api/OO" class="extiw" title="wmdoc:VisualEditor/master/">API Documentation</a></li> <li><a rel="nofollow" class="external text" href="https://www.npmjs.com/package/@types/oojs">Community-created TypeScript definitions</a> for OOjs (work in JavaScript projects as well in popular IDEs).</li></ul> <style data-mw-deduplicate="TemplateStyles:r7217283">.mw-parser-output table.ambox{margin:0 10%;width:unset;border:1px solid var(--border-color-base,#a2a9b1);border-left:10px solid var(--border-color-progressive,#36c);background-color:var(--background-color-neutral-subtle,#f8f9fa);box-sizing:border-box}.mw-parser-output table.ambox+table.ambox,.mw-parser-output table.ambox+link+table.ambox,.mw-parser-output table.ambox+style+table.ambox{margin-top:-1px}.mw-parser-output .ambox td.mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox th.mbox-text,.mw-parser-output .ambox td.mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox td.mbox-image{padding:2px 0 2px 0.5em}.mw-parser-output .ambox td.mbox-imageright{padding:2px 0.5em 2px 0}.mw-parser-output table.ambox-notice{border-left-color:var(--border-color-progressive,#36c)}.mw-parser-output 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typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ec/OOjs_UI_icon_information-progressive.svg/40px-OOjs_UI_icon_information-progressive.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ec/OOjs_UI_icon_information-progressive.svg/60px-OOjs_UI_icon_information-progressive.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ec/OOjs_UI_icon_information-progressive.svg/80px-OOjs_UI_icon_information-progressive.svg.png 2x" data-file-width="20" data-file-height="20" /></span></span></div></td><td class="mbox-text"><div class="mbox-text-span"><a class="mw-selflink selflink">OOjs</a> is maintained by <b>the <a href="/wiki/Editing" class="mw-redirect" title="Editing">Editing</a> department</b>. <p>Get help: </p> <ul><li><span typeof="mw:File"><a href="/wiki/File:OOjs_UI_icon_speechBubbles-ltr-progressive.svg" class="mw-file-description"><img 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