Regular expression for length validation in email address.

Question

We have a textbox which accepts comma separated email address. The regular expression is

^(\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*\s*[,]?\b)*$.

However now I am unable to add a length validation to this expression. Each email address should not be more than 150 characters. I have tried

^((\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)){1,150}\s*[,]?\b)*$. 

But it doesn't work. Can you please modify the regex so that it also implements this validation too.

Answer 1

^([a-zA-Z][\w\.-]*[a-zA-Z0-9]@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z]){0,70}$

Answer 2

Why use a regexp when you can simply check the length of the string? If you must, use a second regexp:

^.{1,150}$

Answer 3

I would rather not complicate this regex further and add explicit length check before checking that e-mail matches. In JavaScript it will be something like the following:

function validateEmail(email) {
    var regex = /^(\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*\s*[,]?\b)*$/;
    // 20 is used instead of 150 for sake of example
    return email.length <= 20 && regex.test(email);
}
// validateEmail("[email protected]") == true
// validateEmail("[email protected]") == false

By the way, dot after $ in your regex seems to be a mistake, so I skipped it in my snippet.