Validate Numeric input javascript

// Validate Numeric Input

// onKeyPress="javascript:return MoveCursorNext(event,this.id);"
function MoveCursorNext(evt, num) {
    var charCode = (evt.which) ? evt.which : event.keyCode


    if (charCode > 31 && (charCode < 48 || charCode > 57))
        return false;
}