Validating email that has @something.co.uk

Question

I have the following regex options:

let emailValid = "/^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$/"
    emailValid = "^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$"
    emailValid = `/^(([^<>()[\]\\.,;:\s@"]+(\.[^<>()[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/`
    emailValid =  "/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/"

And none are able to consistently reject @somethingcouk while accepting @something.co.uk

The advice given here is just plain wrong https://www.w3resource.com/javascript/form/email-validation.php

It suggests /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/ which, according to them, should accept [email protected], but in my case it does not accept [email protected].

I'd like not to spend 3 days learning the regex to do this, when various tutorials and stack overflow answers are already given. What am I doing wrong here?

Does inputting these as a variable, without using match(), as some places suggest, affect the functionality?

Answer 1

The options you list are all strings.

While there are cases where you can convert a string to a regular expression, your approach is breaking all the escape characters (because a \ starts an escape sequence in both strings and regular expressions.

Use a regular expression literal instead:

const emailValid = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/;

Possibly not that one though because top-level domain names are no longer restricted to 2 or 3 characters. There's a reason that the email address validation browsers apply to input type=email generally isn't any more complex than "Contains an @ sign".

Answer 2

I have made this long time ago and this also accept email address for ip domain like [email protected]

function checkEmailPattern(str) {
    const pattern = /^([^\.\_\-\@])+([^\.\@\_\-])*((([^\d\@]){0,1})[a-z0-9]{2,}){0,1}((@([a-zA-Z]{2,})+(\.([a-z]{2,})){1,2}|@(\d{3}.){1,3})|(@([0-9]{1,3})+(\.([0-9]{1,3})){3}))$/;

    return pattern.test(str.toLowerCase());
}

let value1 = '[email protected]';

console.log(checkEmailPattern(value1)); // true