To check whether a checkbox is checked, try to run the following code. It returns true if the checkbox is checked, else false −
Example
<html>
<head>
<script>
function myFunction(){
var result = document.getElementById("check").checked;
alert(result);
}
</script>
</head>
<body>
<label><input id="check" type="checkbox" >One</label><br>
<button onclick="myFunction()">Check value</button>
</body>
</html>