---
title: XMLHttpRequest.onreadystatechange
slug: Web/API/XMLHttpRequest/onreadystatechange
translation_of: Web/API/XMLHttpRequest/onreadystatechange
---
<div>{{APIRef}}</div>

<p>UN <a href="/en-US/docs/Web/API/EventHandler" title="A possible way to get notified of Events of a particular type (such as click) for a given object is to specify an event handler using:"><code>EventHandler</code></a>  che è invocato ogni volta che l'attributo <code>readyState </code>cambia. la callback è invocata dal thread dell'interfaccia utente. </p>

<p>La proprietà <strong><code>XMLHttpRequest.onreadystatechange</code></strong>  contiene l<code>'event handler </code>che deve essere invocato quando l'evento {{event("readystatechange")}} si verifica, ovvero ogni volta in cui la proprietà {{domxref("XMLHttpRequest.readyState", "readyState")}} del {{domxref("XMLHttpRequest")}} viene modificata.</p>

<div class="warning">
<p><strong>Warning:</strong> This should not be used with synchronous requests and must not be used from native code. .</p>
</div>

<p>L'evento <code>readystatechange</code> non si verificherà se una richiesta <code>XMLHttpRequest</code> viene cancellata utilizzando il metodo <a href="/en-US/docs/Web/API/XMLHttpRequest/abort">abort()</a>.</p>

<div class="note">
<p>UPDATE: it's firing in the latest version of browsers (Firefox 51.0.1, Opera 43.0.2442.991, Safari 10.0.3 (12602.4.8), Chrome 54.0.2840.71, Edge, IE11). Example <a href="https://jsfiddle.net/merksam/ve5oc0gn/">here</a> - just reaload page few times.</p>
</div>

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

<pre class="syntaxbox"><em>XMLHttpRequest</em>.onreadystatechange = <em>callback</em>;</pre>

<h3 id="Values">Values</h3>

<ul>
 <li><code><em>callback</em></code> è la funzione che viene eseguita quando  <code>readyState</code> cambia.</li>
</ul>

<h2 id="Example" name="Example">Example</h2>

<pre class="brush: js">var xhr = new XMLHttpRequest(),
    method = "GET",
    url = "https://developer.mozilla.org/";

xhr.open(<em>method</em>, <em>url</em>, true);
xhr.onreadystatechange = function () {
  if(xhr.readyState === XMLHttpRequest.DONE &amp;&amp; xhr.status === 200) {
    console.log(xhr.responseText);
  }
};
xhr.send();</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('XMLHttpRequest', '#handler-xhr-onreadystatechange')}}</td>
   <td>{{Spec2('XMLHttpRequest')}}</td>
   <td>WHATWG living standard</td>
  </tr>
 </tbody>
</table>

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

<p>{{CompatibilityTable}}</p>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Edge</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatChrome(1)}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoDesktop(1.0)}}</td>
   <td>{{CompatIe(7)}}<sup>[1]</sup></td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatSafari(1.2)}}</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>Edge</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>{{CompatUnknown}}</td>
   <td>1.0</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<p>[1] Internet Explorer version 5 and 6 supported ajax calls using <code>ActiveXObject()</code>.</p>