jQuery numeric input mask
<p>I'm trying to do a simple integer numeric input mask without having to include an entire plugin like <a href="http://digitalbush.com/projects/masked-input-plugin/" rel="nofollow">Digital Bush's masked input</a>.</p>

<p>Here's the code I've "repurposed" from another stackoverflow question:</p>

<pre><code>$('input[name=Qty]').keyup(function() {
    var theEvent = evt || window.event;
    var key = theEvent.keyCode || theEvent.which;
    key = String.fromCharCode( key );
    var regex = '[0-9]'; /* Use |\. to include a decimal */
    if( !regex.test(key) ) {
     theEvent.returnValue = false;
     theEvent.preventDefault();
    }
});
</code></pre>

<p>The error is on the first line, where it doesn't know what evt is.<br>
I think I need to use $(this) something.</p>
