Example of JavaScript Generic functions

Hi,

Please refer below javascript functions

<script type="text/javascript">
    function IsEmpty(textbox, errorMessage) {
        if (textbox.value == '') {
            textbox.focus();
            alert(errorMessage);
            return false;
        }
    }

    function IsNumeric(evt) {
        var e = evt || window.event; //window.event is safer, thanks @ThiefMaster
        var charCode = e.which || e.keyCode;
        if (charCode > 31 && (charCode < 47 || charCode > 57))
            return false;
        if (e.shiftKey) return false;
        return true;
    }

    function IsAlphaNumeric(evt) {
        evt = evt || window.event;
        var regex = new RegExp("^[a-zA-Z0-9\b]+$");
        var key = String.fromCharCode(!evt.charCode ? evt.which : evt.charCode);
        if (!regex.test(key)) {
            evt.preventDefault();
            return false;
        }
    }


    function validateEmail(textbox) {
        var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
        if (!filter.test(textbox.value)) {
            alert('Please provide a valid email address');
            textbox.focus;
            return false;
        }
    }
    
</script>