---
title: Array.length
slug: Web/JavaScript/Reference/Global_Objects/Array/length
translation_of: Web/JavaScript/Reference/Global_Objects/Array/length
---
<div>{{JSRef}}</div>

<div>La proprieta' <strong>length</strong> setta o restituisce il numero di elementi in un array. E' un intero a 32 bit, sempre maggiore del piu' grande indice dell'array.</div>

<div> </div>

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

// returns 4</pre>

<h2 id="Descrizione">Descrizione</h2>

<p>Puoi impostare la proprietà <strong>length</strong> di un array per troncare o estendere l'array stesso.</p>

<pre class="brush: js">var a = [1,2,3];
a.length=2;
// a is now [1, 2]

a.length = 10
// a is now [1, 2, undefined × 8]
</pre>

<h3 id="sect1"> </h3>

<h2 id="Esempi">Esempi</h2>

<h3 id="Iterare_su_un_array">Iterare su un array</h3>

<p>Nel seguente esempio, l'array <em>numbers</em> viene iterarato e ciascun elemento viene moltiplicato per 2.</p>

<pre class="brush: js">var numbers = [1, 2, 3, 4, 5];
var length = numbers.length;
for (var i = 0; i &lt; length; i++) {
  numbers[i] *= 2;
}
// numbers is now [2, 4, 6, 8, 10]
</pre>

<h3 id="Specifiche">Specifiche</h3>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specifiche</th>
   <th scope="col">Stato</th>
   <th scope="col">Commento</th>
  </tr>
  <tr>
   <td>{{SpecName('ES1')}}</td>
   <td>{{Spec2('ES1')}}</td>
   <td>Definizione iniziale.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-15.4.5.2', 'Array.length')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-properties-of-array-instances-length', 'Array.length')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-properties-of-array-instances-length', 'Array.length')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="Compatibilità">Compatibilità</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="sect2"> </h2>