On submit form, return false not working

Question

When I submit the form I got an alert message. When I accept the alert it will submit the form anyway. Returning false is ignored. Onclick can not be used. I try with var x = document.forms["form"]["fname"].value; and still same.

<form id="f" method="post" name="form" onsubmit="return validateForm();" action="#">
    <input type="text" name="fname" id="test" />
    <input type="submit" value="submit"/>
</form>
<script type="text/javascript">
        function validateForm() {
            var x = document.getElementById('test').value;
            if (x == null || x == 0 || x == "0") {
                alert("Stop");
                return false;
            }
        }
    </script>

Answer 1

Instead of <input type="submit" value="submit"/> use <input type="button" value="Submit" onclick='validateForm()'/>.

In your JS:

<script type="text/javascript">
    function validateForm() {
        var x = document.getElementById('test').value;
        if (x == null || x == 0 || x == "0") {
            alert("Stop");
        }
        else
            document.form.submit();
    }
</script>