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Asked: 2026-05-13T11:25:28+00:00

I’ve faced strange problem. While user change of check box input element on form

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I’ve faced strange problem. While user change of check box input element on form produces adequate event programmatic change don’t. How should I face this challenge? Code following:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title></title>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.js"></script>
  <script type="text/javascript">
    jQuery(document).ready(
      function() {        
        jQuery("#cb").change(
          function() {
            alert("Changed!"); 
            return true;
          }
        );
        jQuery("#b").click(
          function() {
            var newState = !jQuery("#cb").attr('checked');
            jQuery("#cb").attr('checked', newState);
          });
      });
  </script>
</head>
<body>
  <form action="#">
    <p>
      <input type="button" id="b" />
      <input type="checkbox" id="cb" />
    </p>
  </form>
</body>
</html>

Update
I do not control element changes, I just need to handle them. It’s general-propose code I write.

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1 Answer

  1. Editorial Team

    It’s impossible to track object’s state within javascript language as it could be done in Objective-C (KVO). Nor it possible using DOM features – DOM do not fire events on every property change – instead it only fires events on certain user actions: mouse clicks, key presses, or page life cycle and their derivatives.

    One could achieve that only firing event every time she modifies some property. Certainly this could be encapsulated in a function as AnthonyWJones had mentioned.

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