Revision 418523 of New in JavaScript 1.6

<p>JavaScript 1.6 introduces several new features: E4X, several new <code>Array</code> methods, and Array and String generics.</p>
<p>JavaScript 1.6 is supported in <a href="/en-US/docs/Firefox_1.5_for_developers" title="Firefox_1.5_for_developers">Firefox 1.5</a> and later.</p>


<div class="warning">
  <h2 id="E4X_(since_deprecated)">E4X (since deprecated)</h2>
</div>

<p>ECMAScript for XML (<a href="/en-US/docs/E4X" title="E4X">E4X</a>) is a powerful technology for creating and processing <a href="/en-US/docs/XML" title="XML">XML</a> content within <a href="/en-US/docs/JavaScript" title="JavaScript">JavaScript</a>. We're going to continue to improve our E4X support, including adding transparent integration with the existing <a href="/en-US/docs/DOM" title="DOM">DOM</a>, but developers who are building XML-based web applications can benefit from E4X support in Firefox 1.5.</p>
<p>You can still use the standard MIME type when using E4X:</p>

<pre class="brush: html">
&lt;script type="text/javascript"&gt;
</pre>
<p>However, E4X syntax may conflict with the common practice of putting scripts into HTML comments (<code>&lt;!--...--&gt;</code>) to hide them from old browsers. E4X may also conflict with the more modern practice of putting scripts within XML CDATA sections (<code>&lt;![CDATA{{mediawiki.external('...')}}]&gt;</code>) to allow the symbols "&lt;" and "&gt;" in the script (note that this does not apply to HTML). If you see inexplicable syntax errors, add "; e4x=1" to the MIME type:</p>

<pre class="brush: html">
&lt;script type="text/javascript; e4x=1"&gt;
</pre>
<p>Note that scripts in extensions always treat HTML comments as E4X literals. That is, the "e4x=1" is implicit.</p>
<p>E4X is documented in <a href="/en-US/docs/E4X/Processing_XML_with_E4X" title="E4X/Processing_XML_with_E4X">Processing XML with E4X</a>.</p>



<h2 id="Array_extras">Array extras</h2>
<p>There are seven new <code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array" title="JavaScript/Reference/Global_Objects/Array">Array</a></code> methods that can be separated into two categories, item location methods and iterative methods. The item location methods are:</p>
<ul>
  <li><code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/indexOf" title="JavaScript/Reference/Global_Objects/Array/indexOf">indexOf()</a></code> - returns the index of the given item's first occurrence.</li>
  <li><code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/lastIndexOf" title="JavaScript/Reference/Global_Objects/Array/lastIndexOf">lastIndexOf()</a></code> - returns the index of the given item's last occurrence.</li>
</ul>
<p>The iterative methods are:</p>
<ul>
  <li><code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/every" title="JavaScript/Reference/Global_Objects/Array/every">every()</a></code> - runs a function on items in the array while that function is returning true. It returns true if the function returns true for every item it could visit.</li>
  <li><code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/filter" title="JavaScript/Reference/Global_Objects/Array/filter">filter()</a></code> - runs a function on every item in the array and returns an array of all items for which the function returns true.</li>
  <li><code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/forEach" title="JavaScript/Reference/Global_Objects/Array/forEach">forEach()</a></code> - runs a function on every item in the array.</li>
  <li><code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/map" title="JavaScript/Reference/Global_Objects/Array/map">map()</a></code> - runs a function on every item in the array and returns the results in an array.</li>
  <li><code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/some" title="JavaScript/Reference/Global_Objects/Array/some">some()</a></code> - runs a function on items in the array while that function returns false. It returns true if the function returns true for any item it could visit.</li>
</ul>

<p>For more information see <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Working_with_Arrays#Introduced_in_JavaScript_1.6" title="JavaScript/Guide/Working_with_Arrays#Introduced_in_JavaScript_1.6">Working with Arrays</a>, or consult Nicholas C. Zakas' article, <a class="external" href="https://www.webreference.com/programming/javascript/ncz/column4/index.html">Mozilla's New Array Methods</a>.</p>



<h2 id="Array_and_String_generics">Array and String generics</h2>
<ul>
  <li><a href="https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array#Array_generic_methods" title="https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array#Array_generics">Array generics</a></li>
  <li><a href="https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String#String_generic_methods" title="https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String#String_generics">String generics</a></li>
</ul>



<h2>For each ... in</h2>
<p><a href="/en-US/docs/JavaScript/Guide/Statements#for_each...in_Statement" title="JavaScript/Guide/Statements#for_each...in_Statement">for each ... in</a> was introduced for iterating over an object's (or array's) property values instead of its keys/properties. This construct is also used in <a href="/E4X" title="E4X">E4X</a>.</p>



<h2 id="See_also">See also</h2>
<ul>
  <li><a href="/en-US/docs/JavaScript/Guide/Predefined_Core_Objects#Working_with_Array-like_objects" title="https://developer.mozilla.org/en/JavaScript/Guide/Predefined_Core_Objects#Working_with_Array-like_objects">Working with Array-like objects</a>.</li>
<li><a href="/en-US/docs/tag/JavaScript" title="Articles tagged: JavaScript | MDN">Articles tagged: JavaScript</a></li>
</ul>


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