Question

I have to check a users input against their in-putted email to check if they are too similar, if they are I need to throw an error. For example;

“The user name can’t be too similar to the email address e.g. if the email address is [e-mail] the username can’t be charlie.”

How could I go about doing this?

EDIT: I want to check the username against the first section of the email address, the section before the @

Answer 1

var email, username;
if (username === email.split('@')[0]) {
  alert('failed');
}

This will compare the username with the username part of email.

Edit:
The point is you could get the username part from the email by email.split('@')[0], then how similar is defined by you.

function is_similar (str1, str2) {
    // implement your similar logic here
    // return true or false
}