set input to type phone number code example
Example 1: how to validate mobile number in html form
<div>
<label for="phone">Enter your phone number:</label>
<input type="tel" id="phone" name="phone" pattern="+94[7-9]{2}-[0-9]{3}-[0-9]{4}" value="+94">
</div>
Example 2: html textbox pattern mobile number
<input type="text" name="Phone Number" pattern="[7-9]{1}[0-9]{9}"
title="Phone number with 7-9 and remaing 9 digit with 0-9">