Firefox error: Unable to check input because the pattern is not a valid regexp: invalid identity escape in regular expression

Question

I\'m using regex pattern matching for HTML5 form validation. The latest version of Firefox gives me an error. I only started seeing this in Firefox 46. I don\'t think th

Answer 1

This is due to the following change: Bug 1227906 - HTML pattern attribute should set u flag for regular expressions

As someone has already said, you don't have to escape those characters. Just use:

<input pattern="[@%]">