How to find checked event in a checkbox using jquery? -

i trying execute function on clicking check box. using following code not working can find whats problem code?

$('#selectall').click(function(){      alert("hi"); });

html

<th><input type="checkbox" name="selectl" value="on" id="selectall"/></th>

$(function(){     $('#selectall').change(function(){          alert("value changed");     }); });

Expalin