<pclass="arguement"><strong>handler()</strong>The function to be invoked.</p>
</li></ul>
<divclass="longdesc">
<p>Whenever an Ajax request is about to be sent, jQuery checks whether there are any other outstanding Ajax requests. If none are in progress, jQuery triggers the <code>ajaxStart</code> event. Any and all handlers that have been registered with the <code>.ajaxStart()</code> method are executed at this time.</p>
<p>To observe this method in action, we can set up a basic Ajax load request:</p>
<p>We can attach our event handler to any element:</p>
<pre>$('.log').ajaxStart(function() {
$(this).text('Triggered ajaxStart handler.');
});</pre>
<p>Now, we can make an Ajax request using any jQuery method:</p>
<pre>$('.trigger').click(function() {
$('.result').load('ajax/test.html');
});</pre>
<p>When the user clicks the button and the Ajax request is sent, the log message is displayed.</p>
<p><strong>Note:</strong> Because <code>.ajaxStart()</code> is implemented as a method of jQuery object instances, we can use the <code>this</code> keyword as we do here to refer to the selected elements within the callback function.</p>
