[jquery] Validate that text field is numeric usiung jQuery

This should work. I would trim the whitespace from the input field first of all:

if($('#Field').val() != "") {
    var value = $('#Field').val().replace(/^\s\s*/, '').replace(/\s\s*$/, '');
    var intRegex = /^\d+$/;
    if(!intRegex.test(value)) {
        errors += "Field must be numeric.<br/>";
        success = false;
    }
} else {
    errors += "Field is blank.</br />";
    success = false;
}