/* Here is the complete code */
<html>
<head>
<title> Check - Uncheck all checkbox </title>
</head>
<script language="javascript">
function checkedAll (frm1)
{
var aa= document.getElementById('frm1');
for (var i =0; i < aa.elements.length; i++)
{
aa.elements[i].checked = true;
}
}
function uncheckedAll (frm1)
{
var aa= document.getElementById('frm1');
for (var i =0; i < aa.elements.length; i++)
{
aa.elements[i].checked = false;
}
}
</script>
<body>
Select : <a href="#" onclick="checkedAll();">All</a>/<a href="#" onclick="uncheckedAll();">None</a> <br/>
<form id="frm1">
<input id="chk" type="checkbox"> Java <br/>
<input id="chk" type="checkbox"> J2ee <br/>
<input id="chk" type="checkbox"> Javascript <br/>
<input id="chk" type="checkbox"> Linux <br/>
<input id="chk" type="checkbox"> Oracle <br/>
</form>
</body>
</html>
Output