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Editorial Team
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Asked: 2026-05-27T09:25:04+00:00

Why does the following jQuery code cause my browser to hang? Caution: do not

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Why does the following jQuery code cause my browser to hang?

Caution: do not run this unless you are prepared to force quit your browser

<!DOCTYPE HTML> 
  <title>Simple clone</title> 
  <script type="text/javascript" src="jquery.js"></script> 

  <div>
    <script>$('div').clone().appendTo('body');</script>
  </div>

Edit

For those in the “infinite loop” camp, that should not be an issue. A perfectly safe (non-jQuery) version is:

  <div>div
    <script>
      var el = document.getElementsByTagName('div')[0];
      document.body.appendChild(el.cloneNode(true));
    </script>
  </div>

So the issue is specifically related to how jQuery does clones.

Edit 2

It seems that jQuery causes script elements in clones to be executed. That isn’t standard behaviour and is something about how jQuery does clones that is quite unexpected.

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1 Answer

  1. Editorial Team

    Because you’re cloning a div that has inside of it a script that says to clone all divs. The original div’s script that says to clone all divs is cloned too, and so on, ad infinitum

    Of course you could do:

      <script type="text/javascript" src="jquery.js"></script> 
  <script type="text/javascript">
     $(function() {
        $('div').clone().appendTo('body');
     });
  </script>

  <div>
    Safe Now
  </div>
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