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---
title: Array.prototype.keys()
slug: Web/JavaScript/Reference/Global_Objects/Array/keys
translation_of: Web/JavaScript/Reference/Global_Objects/Array/keys
---
<div>{{JSRef}}</div>
<p>Il metodo <code><strong>keys()</strong></code> ritorna un nuovo oggetto <code><strong>Array Iterator</strong></code> contenente le chiavi di ogni indice dell'array.</p>
<pre class="brush: js">var arr = ['a', 'b', 'c'];
var iterator = arr.keys();
console.log(iterator.next()); // { value: 0, done: false }
console.log(iterator.next()); // { value: 1, done: false }
console.log(iterator.next()); // { value: 2, done: false }
console.log(iterator.next()); // { value: undefined, done: true }
</pre>
<h2 id="Sintassi">Sintassi</h2>
<pre class="syntaxbox"><var>arr</var>.keys()</pre>
<h3 id="Valore_di_ritorno">Valore di ritorno</h3>
<p>Un nuovo oggetto {{jsxref("Array")}}.</p>
<h2 id="Esempi">Esempi</h2>
<h3 id="I_Key_iterator_non_ignorano_gli_elementi_vuoti">I Key iterator non ignorano gli elementi vuoti</h3>
<pre class="brush: js">var arr = ['a', , 'c'];
var sparseKeys = Object.keys(arr);
var denseKeys = [...arr.keys()];
console.log(sparseKeys); // ['0', '2']
console.log(denseKeys); // [0, 1, 2]
</pre>
<h2 id="Specifiche">Specifiche</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specifica</th>
<th scope="col">Stato</th>
<th scope="col">Commenti</th>
</tr>
<tr>
<td>{{SpecName('ES2015', '#sec-array.prototype.keys', 'Array.prototype.keys')}}</td>
<td>{{Spec2('ES2015')}}</td>
<td>Initial definition.</td>
</tr>
<tr>
<td>{{SpecName('ESDraft', '#sec-array.prototype.keys', 'Array.prototype.keys')}}</td>
<td>{{Spec2('ESDraft')}}</td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="Browser_compatibility">Browser compatibility</h2>
<div>
<p>{{Compat("javascript.builtins.Array.keys")}}</p>
</div>
<h2 id="Vedi_anche">Vedi anche</h2>
<ul>
<li>{{jsxref("Array.prototype.values()")}}</li>
<li>{{jsxref("Array.prototype.entries()")}}</li>
<li><a href="/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">Iteration protocols</a></li>
</ul>
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