Revision 652263 of New in JavaScript

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<p>This chapter contains information about JavaScript's version history and implementation status for Mozilla/SpiderMonkey-based JavaScript applications, such as Firefox.</p>
<h2 id="ECMAScript_versions">ECMAScript versions</h2>
<dl>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/Language_Resources">Language resources</a></dt>
 <dd>
  Learn more about the ECMAScript standards on which the JavaScript language is based on.</dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/ECMAScript_5_support_in_Mozilla">ECMAScript 5 support</a></dt>
 <dd>
  Implementation status for ECMA-262 Edition 5 in Firefox.</dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/ECMAScript_6_support_in_Mozilla">ECMAScript 6 support</a></dt>
 <dd>
  Implementation status for ECMA-262 Edition 6 in Firefox.</dd>
</dl>
<h2 id="JavaScript_release_notes">JavaScript release notes</h2>
<dl>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/Firefox_JavaScript_changelog">Firefox JavaScript changelog</a></dt>
 <dd>
  See this changelog for JavaScript features implemented in Firefox 5 and later.</dd>
 <dt>
  Chrome JavaScript changelog</dt>
 <dd>
  (TODO). See this changelog for JavaScript features implemented in Chrome releases.</dd>
</dl>
<h2 id="JavaScript_versions">JavaScript versions</h2>
<p><strong>Deprecated</strong> ({{deprecated_inline()}}). The explicit versioning and opt-in of language features was Mozilla-specific and <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=867609">is in the process of of being removed</a>. Firefox 4 was the last version which referred to an JavaScript version (1.8.5). With new ECMA standards, JavaScript language features are now often mentioned with their initial definition in ECMA-262 Editions such as Edition 6 (ES6).</p>
<p>JavaScript was released as version 1.0 in March 1996 in Netscape Navigator 2.0 and Internet Explorer 2.0.</p>
<dl>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/1.1">JavaScript 1.1</a></dt>
 <dd>
  Version shipped in Netscape Navigator 3.0. Released on August 19, 1996.</dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/1.2">JavaScript 1.2</a></dt>
 <dd>
  Version shipped in Netscape Navigator 4.0-4.05. Released on June 11, 1997.</dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/1.3">JavaScript 1.3</a></dt>
 <dd>
  Version shipped in Netscape Navigator 4.06-4.7x. Released on October 19, 1998.<br />
  Standardization work to be compliant with ECMA-262 1st and 2nd Edition.</dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/1.4">JavaScript 1.4</a></dt>
 <dd>
  Version shipped in Netscape's server side JavaScript. Released in 1999.</dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/1.5">JavaScript 1.5</a></dt>
 <dd>
  Version shipped in Netscape Navigator 6.0 and Firefox 1.0. Release on November 14, 2000.<br />
  Standardization work to be compliant with ECMA-262 3rd Edition.</dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/1.6">JavaScript 1.6</a></dt>
 <dd>
  Version shipped in Firefox 1.5. Released in November 2005.<br />
  Includes ECMAScript for XML (E4X), new <code>Array</code> methods plus <code>String</code> and <code>Array</code> generics.</dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/1.7">JavaScript 1.7</a></dt>
 <dd>
  Version shipped in Firefox 2. Released in October 2006.<br />
  Includes generators, iterators, array comprehensions, <code>let</code> expressions, and destructuring assignment.</dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/1.8">JavaScript 1.8</a></dt>
 <dd>
  Version shipped in Firefox 3. Released in June 2008.<br />
  Includes expression closures, generator expressions and <code>Array.reduce()</code></dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/1.8.1">JavaScript 1.8.1</a></dt>
 <dd>
  Version shipped in Firefox 3.5. Released on <span class="st">June 30, 2009.<br />
  Includes the TraceMonkey JIT and supports native JSON.</span></dd>
 <dt>
  JavaScript 1.8.2</dt>
 <dd>
  Version shipped in Firefox 3.6. Released June 22, 2009.<br />
  Includes only minor changes.</dd>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/1.8.5">JavaScript 1.8.5</a></dt>
 <dd>
  Version shipped in Firefox 4. Released July 27, 2010.<br />
  Includes many new features for ECMA-262 Edition 5 compliance.<br />
  This is the last JavaScript version.</dd>
</dl>
<h2 id="Features_still_requiring_version_opt-in">Features still requiring version opt-in</h2>
<dl>
 <dt>
  <a href="/en-US/docs/Web/JavaScript/Reference/Statements/let"><code>let</code> statement</a></dt>
 <dd>
  The <code>let</code> statement requires the JavaScript version 1.7 opt-in.</dd>
</dl>