What error am I making when attempting to validate an email address with RegExp?

I have been attempting to verify the format of an email address using the script below, but I seem to be making a mistake somewhere. When I try to match the reg_1 pattern with str_1, str_2, str_3, I consistently get a false result. Can anyone help me understand why?

var reg_1 = /^[a-zA-Z][0-9_.][@]{1}[a-zA-Z0-9][.]{1}[a-zA-Z0-9]$/;
var id_1 = "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="2152544940484d4654515540111261464c40484d0f424e4c">[email protected]</a>";
var id_2 = "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="3a5d4f4a4e5b14494f525b53567a485f5e535c5c14595557">[email protected]</a>";
var id_3 = "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="e390968b828a8fbc8496939782d3d0a38c958acd808c8e">[email protected]</a>";

document.write(reg_1.test(id_1));
document.write("<br / >" + reg_1.test(id_2));
document.write("<br / >" + reg_1.test(id_3));
javascriptregex

Answer №1

Your grasp of the character class notation [...] appears to be a bit off. To clarify, [a-zA-Z][0-9_.] signifies "a letter from a to z or from A to Z, followed by a digit from 0 to 9 or underscore _ or dot .".

Based on your intentions, it seems like you're aiming for:

var reg_1 = /^[a-zA-Z0-9_.]+@[a-zA-Z0-9]+\.[a-zA-Z0-9]+$/;

In addition to necessary modifications, I tidied things up a bit: specifically, I replaced [@] with just @ (no need for a character class) and [.] with \. (because you want to match a dot and not any character), and I omitted the {1} since it's implied anyway.

(Keep in mind that this regex isn't a catch-all for validating e-mail addresses. The complexity of e-mail addresses necessitates actually sending an e-mail to confirm its validity!)

Answer №2

One key aspect to note is that you are searching for a sequence that starts with two specific characters and is followed by an @ symbol, yet none of the email addresses you have provided follow this pattern.

Answer №3

Avoid making this mistake. I was just in the middle of drafting a blog post explaining why this method is not effective: How to Properly Validate an Email Address

Simply use a regular expression like the one below for better results:

var emailRegex = /.+@.+\..+/;
console.log(emailRegex.test("<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="98edebfdead8fde0f9f5e8f4fdb6fbf7f5">[email protected]</a>")); // Output: "true"
console.log(emailRegex.test("www.example.com")); // Output: "false"

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