JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://raw.githubusercontent.com/digitalBush/jquery.maskedinput/master/src/jquery.maskedinput.js"></script>
<input type="text" id="txt_PhoneNumber" />

<button type="button" id="btn">9</button>

JavaScript

$('#txt_PhoneNumber').mask('(999) 999-9999');

$('#btn').click(function() {
    $("#txt_PhoneNumber").val(function(i, val) {
        return val + '9';
    }).trigger('input');
});