JSFiddle - React, Tailwind, and code Playground

HTML

<script>
      function calcular(operacao) {

        var xmlhttp;
  
        if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari

          xmlhttp = new XMLHttpRequest();
        } else {// code for IE6, IE5
  
          xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
  
        } xmlhttp.onreadystatechange = function() {
          if (xmlhttp.readyState==4 && xmlhttp.status==200) {

document.getElementById("Resp").innerHTML=xmlhttp.responseText;
          }
        }
        xmlhttp.open("POST", "https://arraysoftware.in/" ,true);
      

        xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");

        xmlhttp.send("operacao=" + operacao + "&v1=" + document.getElementById("v1").value + "&v2=" + document.getElementById("v2").value );
      }
    </script>


    <h2>A JACA</h2>
   
    <div id="Resp"></div>

<input id="v1"> <p> <center> + </center> <p> <input id="v2">
    
    <button type="button" onclick="calcular('somar')">Somar</button>