how to write the java script code using custom control in as

Question

how to write the java script code using custom control in asp.net?

 

i am using this code in aspx page but i want to use this code  using custom control so how to write this?

 

please explain in steps..

<script type="text/javascript">
function fncheck(me) {
me.checked = true;
var chkary = document.getElementsByTagName('input');
for (i = 0; i < chkary.length; i++) {
if (chkary[i].type == 'checkbox') {
if (chkary[i].id != me.id)
chkary[i].checked = false;
}
}
}
</script></head>