title: jQuery numeric input mask
body: <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 noreferrer">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>