JavaScript: Difference between revisions

| logo = <!-- Do not add unofficial logo, per [[Talk:JavaScript/Archive 5#Why is the unofficial logo present?]] -->

| scope = [[Scope (computer science)|lexical]]

'''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]].

The goal was a "language for the masses",<ref name="EichVideo" /> "to help nonprogrammers create dynamic, interactive [[website|Web sites]]".<ref>"Netscape Communications Corp.", Browser enhancements. Encyclopædia Britannica 2006 Ultimate Reference Suite DVD</ref> Netscape management soon decided that the best option was for Eich to devise a new language, with syntax similar to Java and less like Scheme or other extant [[scripting language]]s.<ref name="looklikejava" /><ref name="origin" /> Although the new language and its [[Interpreter (computing)|interpreter]] implementation were called LiveScript when first shipped as part of a Navigator [[beta software|beta]] in September 1995, the name was changed to JavaScript for the official release in December.<ref name="origin" /><ref name="press_release" /><ref name="techvision">{{cite web | archive-url=https://web.archive.org/web/20080208124612/https://wp.netscape.com/comprod/columns/techvision/innovators_be.html | archive-date=February 8, 2008 | title=TechVision: Innovators of the Net: Brendan Eich and JavaScript | url=https://wp.netscape.com/comprod/columns/techvision/innovators_be.html }}</ref><ref name="wired2024">{{cite magazine |last1=Han |first1=Sheon |title=JavaScript Runs the World—Maybe Even Literally |url=https://www.wired.com/story/javascript-runs-the-world-maybe-literally/ |magazine=Wired |date=4 March 2024 |access-date=21 August 2024}}</ref>

Initial attempts at promoting server-side JavaScript usage were [[Netscape Enterprise Server]] and [[Microsoft]]'s [[Internet Information Services]],<ref>{{cite web |date=December 11, 1998 |title=Server-Side JavaScript Guide |url=https://docs.oracle.com/cd/E19957-01/816-6411-10/contents.htm |url-status=live |archive-url=https://web.archive.org/web/20210311173120/https://docs.oracle.com/cd/E19957-01/816-6411-10/contents.htm |archive-date=March 11, 2021 |access-date=May 8, 2021 |website=oracle.com |publisher=[[Oracle Corporation]]}}</ref><ref>{{cite web|last1=Clinick|first1=Andrew|title=Introducing JScript .NET|url=https://msdn.microsoft.com/en-us/library/ms974588.aspx|website=Microsoft Developer Network|publisher=Microsoft|access-date=April 10, 2018|date=July 14, 2000|quote=[S]ince the 1996 introduction of JScript version 1.0 ... we've been seeing a steady increase in the usage of JScript on the server—particularly in Active Server Pages (ASP)|archive-date=November 10, 2017|archive-url=https://web.archive.org/web/20171110201649/https://msdn.microsoft.com/en-us/library/ms974588.aspx|url-status=live}}</ref> but they were small niches.<ref name="2009server" /> Server-side usage eventually started to grow in the late 2000s, with the creation of [[Node.js]] and [[List of server-side JavaScript implementations|other approaches]].<ref name="2009server">{{cite web |url=https://readwrite.com/2009/12/17/server-side_javascript_back_with_a_vengeance/ |title=Server-Side JavaScript, Back with a Vengeance |date=December 17, 2009 |website=readwrite.com |access-date=July 16, 2016 |author=Mahemoff, Michael |archive-date=June 17, 2016 |archive-url=https://web.archive.org/web/20160617030219/https://readwrite.com/2009/12/17/server-side_javascript_back_with_a_vengeance/ |url-status=live }}</ref>

The following features are common to all conforming ECMAScript implementations unless explicitly specified otherwise. The number of cited reserved words including keywords is 50-60 and varies depending on the implementation.

Values are cast to strings like the following:<ref name="casting_rules" />

Arrow functions were first introduced in [[w:ECMAScript#6th Edition – ECMAScript 2015|6th Edition – ECMAScript 2015]]. They shorten the syntax for writing functions in JavaScript. Arrow functions are anonymous, so a variable is needed to refer to them in order to invoke them after their creation, unless surrounded by parenthesis and executed immediately.

* {{cite book|last=Zakas|first=Nicholas|title=Principles of Object-Oriented JavaScript|edition=1st|publisher=No Starch Press|year=2014|isbn=978-1593275402}}