The good thing is that the regex will be the same. It's also pretty trivial to write a polyfill to work on old browsers. I've found it's really nice to define t

The good thing is that the regex will be the same. It's also pretty trivial to write a polyfill to work on old browsers. I've found it's really nice to define that in one place then to use it everywhere. Newer users get the HTML5 validation, older ones the Javascript fallback, and everyone gets a second round of checking before it hits the database.