Get checkbox count using JQUERY

Demo Snippet is below

<script src="jquery.js" type="text/javascript">
function chk_box_count(){
var lenChkBox = $("input:checked").length;
alert(lenChkBox);
}
<script>

<form>
<input type="checkbox" name="chk1" >
<input type="checkbox" name="chk1" >
<input type="checkbox" name="chk1" >
<input type="button" value="Check box count" onclick="chk_box_count()" >
</form>