JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//code.jquery.com/ui/1.11.0/themes/smoothness/jquery-ui.css">
<script src="//code.jquery.com/jquery-1.10.2.js"></script>
<script src="//code.jquery.com/ui/1.11.0/jquery-ui.js"></script>
<input type="text" id="txtPhone" name="phone" required data-required="true" class="form-control">
    <button>Ckeck attribute value</button>

JavaScript

$("button").click(function(){
        var myvalue = $("#txtPhone").val();
        if (myvalue == "1") {
             $("#txtPhone").attr("data-required","true");
            //alert(myvalue);
        }
        else {
           $("#txtPhone").attr("data-required","false");
            //alert(myvalue);
        }
});