Try it Editor

<!DOCTYPE html>
<html>
<body>
    <head>
        <title>Onclick Checkbox check all checkbox in Javascript</title>
    </head>
    <input type="checkbox" onClick="toggle(this)" /> Select All<br/>
    <input type="checkbox" name="check" value="check1"> check 1<br/>
    <input type="checkbox" name="check" value="check2"> check 2<br/>
    <input type="checkbox" name="check" value="check3"> check 3<br/>
    <input type="checkbox" name="check" value="check4"> check 4<br/>
    <script>
        function toggle(source) {
            checkboxes = document.getElementsByName('check');
            for (var i = 0, n = checkboxes.length; i < n; i++) {
                checkboxes[i].checked = source.checked;
            }
        }
    </script>
</body>
</html>