you can use something like document.getElementById("variable").checked to see if a checkbox is checked or not -
See the following sample code -
<html>
<head>
<script language="javascript" type="text/javascript">
function exefunction(){
var lfckv = document.getElementById("lifecheck").checked;
alert(lfckv);
}
</script>
</head>
<body>
<label><input id="lifecheck" type="checkbox" >Lives</label>
<button onclick="exefunction()">Check value</button>
</body>
</html>
