JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="txtPhone" name="phone" data-required="true" class="form-control">
    <button>Ckeck attribute value</button>

JavaScript

$("button").click(function(){
  var value = $("#txtPhone").val();
if (value == "1") {
    document.getElementById('txtPhone').setAttribute("data-required","true");
    alert("1");
}
else {
    document.getElementById('txtPhone').setAttribute("data-required","false");
    alert("2");
}
});