Question

I’m trying to use a regular expression validation using .match for email validation and for some reason it only shows invalid even though all formats are followed!

javascript function

function check_email_valid(emails) {
        var emailRegex = '^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$';
        if (emails.match(emailRegex)) {
            jQuery('#<%=Label16.ClientID%>').css('color', 'green');
            jQuery('#<%=Label16.ClientID%>').show();
            jQuery('#<%=Label16.ClientID%>').text("Valid Email!");
        }
        else {
            jQuery('#<%=Label16.ClientID%>').css('color', 'red');
            jQuery('#<%=Label16.ClientID%>').show();
            jQuery('#<%=Label16.ClientID%>').text("Invalid Email!");
        }

Event trigger

 $('#<%=TextBox8.ClientID%>').keyup(function () {
            var email = jQuery('#<%=TextBox8.ClientID%>').val();
            check_email_valid(email);
        });

I keyed in [e-mail] and got “Invalid Email!”. Any idea why?

Answer 1

JavaScript has a slightly different way of defining regex patterns than other languages. They’re not strings, but instead simply start with a slash, end with one, and after that you can specify some flags.

Your pattern is defined like this:

var emailRegex = /^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i;

The i flag at the end of the pattern makes it case insensitive.