Javascript fallback for the HTML5 "pattern" attribute on <input>

Question

I'm using the HTML5 "pattern" attribute for client side validation (please don't tell me about server-side validation, I have that). I want to use a Javascript or jQuery fallback for users using browsers without "pattern" support. What's a good way to do that?

Here's an example input element:

<input type=tel name=contact[phone] id=phone required pattern=^(?:(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?$>

Answer 1

On the submit event of your form (or wherever), validate it using its existing pattern property.

var input = document.getElementsByName('contact[phone]')[0],
    isValid = input.value.search(new RegExp(input.getAttribute('pattern'))) >= 0;

jsFiddle.

You will want to check browser compatibility first to see if it supports the pattern attribute. You can do that with Modernizr.