Yeah, sorry, my comment wasn't really helpful. 

You can look at https://github.com/mozilla/browserid/blob/dev/resources/static/common/js/validation.js for an example of an another regex that is backslash-escaped properly for jshint.

But anyways, I don't really like that this PR will just substitute in yet another regex for the current one on the server side, and that we still have a different way on the client side. (If the server side is a strict superset of the client side test, I'm ok with that. But the client side check we have is already strict on the DNS aspects of the regex (max sizes) that I'd be concerned about). (Side note: gerv's regex is incorrect on those limits).

Also, not to put it on you, but having comprehensive tests of valid and invalid email addresses before changing either the server or client side (preferably shared) would be good. Since HTML5 browsers now implement `input[type=email]` elements, they have test sets already, and they'd be a good base for that.