Editing JavaScript (section)

{{Short description|High-level programming language}}
{{Distinguish|Java (programming language)|Javanese script|ECMAScript}}
{{pp-semi-indef|small=yes}}
{{Use dmy dates|date=March 2024}}
{{Infobox programming language
| name = JavaScript
| logo = <!-- Do not add the unofficial logo, per [[Talk:JavaScript/Archive 5#Why is the unofficial logo present?]] -->
| logo alt = 
| screenshot = JavaScript code.png
| screenshot caption = Screenshot of JavaScript source code
| paradigm = [[Multi-paradigm]]: [[event-driven programming|event-driven]], [[functional programming|functional]], [[imperative programming|imperative]], [[procedural programming|procedural]], [[object-oriented programming|object-oriented]]
| memory management = [[Garbage collection (computer science)|Garbage collection]]
| designer = [[Brendan Eich]] of [[Netscape]] initially; others have also contributed to the [[ECMAScript]] standard
| typing = [[Dynamic typing|Dynamic]], [[Weak typing|weak]], [[Duck typing|duck]]
| implementations = [[V8 (JavaScript engine)|V8]], [[JavaScriptCore]], [[SpiderMonkey (JavaScript engine)|SpiderMonkey]], [[Chakra (JavaScript engine)|Chakra (Deprecated)]]
| influenced = [[ActionScript]], [[ArkTS]], [[AssemblyScript]], [[CoffeeScript]], [[Dart (programming language)|Dart]], [[Haxe]], [[JS++]], [[Opa (programming language)|Opa]], [[TypeScript]]
| license = 
| file extensions = {{flatlist|
* <code>.js</code>
* <code>.mjs</code>
* <code>.cjs</code><ref name="node.js ECMAScript Modules Specification">{{cite web|url=https://github.com/nodejs/node-eps/blob/master/002-es-modules.md|title=nodejs/node-eps|website=GitHub|access-date=2018-07-05|archive-date=2020-08-29|archive-url=https://web.archive.org/web/20200829024713/https://github.com/nodejs/node-eps/blob/master/002-es-modules.md|url-status=live}}</ref>
}}
| file format = 
| wikibooks = JavaScript
| year = {{start date and age|1995|12|4|df=y}}<ref name="press_release">{{Cite press release |url=https://wp.netscape.com/newsref/pr/newsrelease67.html |archive-url=https://web.archive.org/web/20070916144913/https://wp.netscape.com/newsref/pr/newsrelease67.html |archive-date=2007-09-16 |title=Netscape and Sun announce JavaScript, the Open, Cross-platform Object Scripting Language for Enterprise Networks and the Internet |date=December 4, 1995}}</ref>
| latest release version = {{wikidata|property|edit|reference|P548=Q2804309|P348}}
| latest release date = {{start date and age|{{wikidata|qualifier|single|P548=Q2804309|P348|P577}}}}
| latest preview version = {{wikidata|property|edit|reference|P548=Q51930650|P348}}
| latest preview date = {{start date and age|{{wikidata|qualifier|single|P548=Q51930650|P348|P577}}}}
| influenced by = [[Java (programming language)|Java]],<ref name="looklikejava">{{cite book|last=Seibel|first=Peter|title=Coders at Work: Reflections on the Craft of Programming|isbn=978-1-4302-1948-4|quote="Eich: The immediate concern at Netscape was it must look like Java."|url=https://books.google.com/books?id=nneBa6-mWfgC&q=The+immediate+concern+at+Netscape+was+it+must+look+like+Java.&pg=PA141|access-date=December 25, 2018|date=September 16, 2009|publisher=Apress |archive-date=December 24, 2020|archive-url=https://web.archive.org/web/20201224233514/https://books.google.com/books?id=nneBa6-mWfgC&q=The+immediate+concern+at+Netscape+was+it+must+look+like+Java.&pg=PA141|url-status=live}}</ref><ref name="origin" /> [[Scheme (programming language)|Scheme]],<ref name="origin" /> [[Self (programming language)|Self]],<ref>{{cite web|url=https://brendaneich.com/2008/04/popularity/|title = Popularity – Brendan Eich}}</ref> [[AWK]],<ref>{{cite web|title=Brendan Eich: An Introduction to JavaScript, JSConf 2010|website=[[YouTube]]|date=20 January 2013 |quote="Eich: "function", eight letters, I was influenced by AWK."|url=https://www.youtube.com/watch?v=1EyRscXrehw|access-date=November 25, 2019|page=22m|archive-date=August 29, 2020|archive-url=https://web.archive.org/web/20200829024704/https://www.youtube.com/watch?v=1EyRscXrehw|url-status=live}}</ref> [[HyperTalk]]<ref>{{cite book |last=Eich |first=Brendan |authorlink1=Brendan Eich |chapter=Foreword |editor1-last=Goodman |editor1-first=Danny |editor1-link=Danny Goodman |year=1998 |title=JavaScript Bible |edition=3rd |publisher=[[John Wiley & Sons]] |isbn=0-7645-3188-3 |lccn=97078208 |oclc=38888873 |ol=712205M |url-access=registration |url=https://archive.org/details/javascriptbible000good}}</ref>
| website = {{URL|https://ecma-international.org/publications-and-standards/standards/ecma-262/}}
}}

'''JavaScript''' ({{IPAc-en|ˈ|dʒ|ɑː|v|ə|s|k|r|ɪ|p|t|audio=LL-Q1860 (eng)-Flame, not lame-JavaScript.wav}}), often abbreviated as '''JS''', is a [[programming language]] and core technology of the [[World Wide Web]], alongside [[HTML]] and [[CSS]]. <!--don't add dating or decimals: it'll remain 99% indefinitely-->Ninety-nine percent of [[website]]s use JavaScript on the [[Client (computing)|client]] side for [[Web page|webpage]] behavior.<ref name="deployedstats">{{cite web |title=Usage Statistics of JavaScript as Client-side Programming Language on Websites |url=https://w3techs.com/technologies/details/cp-javascript |access-date=2024-02-27 |website=W3Techs }}</ref>

[[Web browser]]s have a dedicated [[JavaScript engine]] that executes the client [[Source code|code]]. These engines are also utilized in some [[Server (computing)|servers]] and a variety of [[Application software|apps]]. The most popular [[runtime system]] for non-browser usage is [[Node.js]].

JavaScript is a [[High-level programming language|high-level]], often [[Just-in-time compilation|just-in-time–compiled]] language that conforms to the [[ECMAScript]] standard.<ref name="tc39">{{cite web|title=ECMAScript 2020 Language Specification|url=https://tc39.es/ecma262/#sec-overview|url-status=live|archive-url=https://web.archive.org/web/20200508053013/https://tc39.es/ecma262/#sec-overview|archive-date=2020-05-08|access-date=2020-05-08}}</ref> It has [[dynamic typing]], [[Prototype-based programming|prototype-based]] [[object-oriented programming|object-orientation]], and [[first-class function]]s. It is [[Programming paradigm|multi-paradigm]], supporting [[Event-driven programming|event-driven]], [[functional programming|functional]], and [[imperative programming|imperative]] [[programming paradigm|programming styles]]. It has [[application programming interface]]s (APIs) for working with text, dates, [[regular expression]]s, standard [[data structure]]s, and the [[Document Object Model]] (DOM).

The ECMAScript standard does not include any [[input/output]] (I/O), such as [[computer network|networking]], [[data storage|storage]], or [[computer graphics|graphics]] facilities. In practice, the web browser or other runtime system provides JavaScript APIs for I/O.

Although [[Java (programming language)|Java]] and JavaScript are similar in name and [[Syntax (programming languages)|syntax]], the two languages are distinct and differ greatly in design.