In jQuery, you can use attr() function to check or unchecked a checkbox dynamically. For example,

A simple checkbox component.

<input type="checkbox" name="checkme">Check Me</input>

1. To display whether this checkbox is checked or not (return true or false).

$('input:checkbox[name=checkme]').is(':checked');

2. To check a checkbox.

$('input:checkbox[name=checkme]').attr('checked',true);

3. To uncheck a checkbox.

$('input:checkbox[name=checkme]').attr('checked',false);

jQuery check / unchecked checkbox example

<html>
<head>
<title>jQuery check / uncheck a check box example</title>
 
<script type="text/javascript" src="jquery-1.3.2.min.js"></script>
 
</head>
 
<body>
 
<h1>jQuery check / uncheck a check box example</h1>
 
<script type="text/javascript">
 
  $(document).ready(function(){
 
    $("#isCheck").click(function () {
 
	alert($('input:checkbox[name=checkme]').is(':checked'));
 
    });
 
    $("#checkIt").click(function () {
 
	$('input:checkbox[name=checkme]').attr('checked',true);
 
    });
 
    $("#UnCheckIt").click(function () {
 
	$('input:checkbox[name=checkme]').attr('checked',false);
 
    });	
 
  });
</script>
</head><body>
 
<input type="checkbox" name="checkme">Check Me</input>
 
<br/>
<br/>
<br/>
 
<input type='button' value='Is Check' id='isCheck'>
<input type='button' value='Check It' id='checkIt'>
<input type='button' value='UnCheck It' id='UnCheckIt'>
 
</body>
</html>
Try Demo
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