html - 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:

1. 7878787878
2. 9898989898
3. 8678678878

These phone numbers are valid, but

1. 1212121212
2. 3434545464
3. 6545432322

are invalid.

Suggest a pattern that can detect valid India phone numbers.

So far, my pattern is [0-9]{10}, but it doesn't check if the first digit is 7, 8, or 9.

Answer 1

How about

<input type="text" pattern="[789][0-9]{9}">