HTML5 phone number validation with pattern

Question

I\'m using HTML5 form validation to validate phone numbers from India.

Phone numbers from India are 10 digits long, and start with 7, 8, or 9.

For example:

Answer 1

This code will accept all country code with + sign

Some countries allow a single "0" character instead of "+" and others a double "0" character instead of the "+". Neither are standard.