JSFiddle - React, Tailwind, and code Playground

JavaScript

var callback = function(data,req){
    alert(data);
};

var ajax=new XMLHttpRequest();

ajax.onreadystatechange=function(){ 
    if( ajax.readyState==4 ){
        callback.call( ajax,ajax.responseText,ajax );
    }
};

ajax.open("POST", "/echo/html/");

ajax.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");

ajax.send("myvar=mylolko");