Revision 1129669 of array.length

<div>{{JSRef}}</div>

<p>The array <code><strong>length</strong></code> property sets or returns the number of elements in an array. It represents an unsigned, 32-bit integer that&nbsp;is always numerically greater than the highest index in the array.</p>

<div>{{js_property_attributes(1, 0, 0)}}</div>

<h2 id="Syntax">Syntax</h2>

<pre class="syntaxbox">
<var>arr</var>.length</pre>

<h2 id="Description">Description</h2>

<p>The value of the <code>length</code> property is an integer with a positive sign and a value less than 2 to the 32nd power (2<sup>32</sup>).</p>

<p>You can set the <code>length</code> property to truncate an array at any time. When you extend an array by changing its <code>length</code> property, the number of actual elements does not increase; for example, if you set <code>length</code> to 3 when it is currently 2, the array still contains only 2 elements. Thus, the <code>length</code> property&nbsp;does not necessarily indicate&nbsp;the number of defined values in the array. See also <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array#Relationship_between_length_and_numerical_properties" title="Relationship between length and numerical properties">Relationship between <code>length</code> and numerical properties</a>.</p>

<h2 id="Examples">Examples</h2>

<h3>Returning the length of an array</h3>

<pre class="brush: js">
var items = ["shoes", "shirts", "socks", "sweaters"];

items.length; 

// returns 4</pre>

<h3 id="Iterating_over_an_array">Iterating over an array</h3>

<p>In the following example, the array <code>numbers</code> is iterated through by looking at the <code>length</code> property. The value in each element is then doubled.</p>

<pre class="brush: js">
var numbers = [1, 2, 3, 4, 5];

for (var i = 0; i &lt; numbers.length; i++) {
  numbers[i] *= 2;
}
// numbers is now [2, 4, 6, 8, 10]
</pre>

<h3 id="Shortening_an_array">Shortening an array</h3>

<p>The following example shortens the array <code>items</code> to a length of 50 if the current length is greater than 50.</p>

<pre class="brush: js">
if (items.length &gt; 50) {
  items.length = 50;
}
</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('ES1')}}</td>
   <td>{{Spec2('ES1')}}</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-15.4.5.2', 'Array.length')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td>&nbsp;</td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-properties-of-array-instances-length', 'Array.length')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>&nbsp;</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-properties-of-array-instances-length', 'Array.length')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td>&nbsp;</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Chrome for Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="See_also">See also</h2>

<ul>
 <li>{{jsxref("Array")}}</li>
</ul>