input field must have 16 digits for mobile code example
Example 1: textbox should accept only numbers till 10 digit using angular
<input type="text" name="country_code" title="Error Message" pattern="[1-9]{1}[0-9]{9}">
Example 2: contact text box accept only till 10 digit in html
<input type="text" maxlength="10" pattern="\d{10}" title="Please enter exactly 10 digits" />