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Editorial Team
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Asked: 2026-05-16T15:35:15+00:00

I want to select all checkbox when i click the top check, below is

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I want to select all checkbox when i click the top check,
below is my code:

run.html

<script language="JavaScript" src="media/js/jquery-1.4.2.min.js"></script>
<script language="javascript">
$("#selectAll").change(function() {
  $(".xxx:checkbox").attr('checked', this.checked);
});
</script>
Select All: <input type="checkbox" id="selectAll"><br />
<br />

One: <input type="checkbox" class="xxx" /><br />
Two: <input type="checkbox" class="xxx" /><br />
Three: <input type="checkbox" class="xxx" />

but why it not work?

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1 Answer

  1. Editorial Team

    Because selectAll does not exist at the time the <script> is run. So $("#selectAll") matches no elements. (jQuery doesn’t warn you when you apply an operation to no elements, it just silently does nothing.)

    Put the <script> below the <input>, or put the binding in a $(document).ready(function() { ... }); block to make the code run at page load time.

    Aside: I would avoid use of the non-standard jQuery selectors like :checkbox wherever possible, as they force the use of the JavaScript Sizzle selector library instead of fast native querySelectorAll. input.xxx[type=checkbox] would be another way of saying it.

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