JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://jquery.bassistance.de/validate/jquery.validate.js"></script>
<input type="text"  required="true" validType="" name="Ph" id="ph" value=""  />

JavaScript

$("#ph").change(function() {
        var a = $("#ph").val();
        var filter = /^[7-9][0-9]{9}$/;

        if (filter.test(a)) {
            alert("valid");
        }
        else {
            alert("not valid");
        }
    });