isValidEmail() JavaScript

is-valid-email.js

// see also is_valid_email() in "strings.php".
String.prototype.isValidEmail = function() {
   // This all are valid accordingly to RFC: !#$%&'*+-/=?^_`{|}~
   // Gmail use + for subadressing. Usage of other special chars in unknown, but they are still valid anyway.
   // Double-dot, however (..) is not allowed.
   return 0 <= this.indexOf("..")
       ? false // email can't have 2 dots at row
       : /^([\w!#$%&'*+\-/=?^_`{|}~]+(?:\.[\w!#$%&'*+\-/=?^_`{|}~]+)*)@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,30}(?:\.[a-z]{2})?)$/i.test(this.trim()); // the longest domain extension in 2015 was ".cancerresearch", and looks like it's not the limit. UPD. how about .travelersinsurance? I set up it the longest domain extension to 30 chars.
}