A CodePen by Nicolas Bevacqua. Bare XMLHttpRequest - A demonstration on how to perform an XMLHttpRequest without any added sauce.

xhr.css

html {
  margin: 20px;
}

div, button {
  font-size: 18px;
  font-family: 'Georgia';
}

#response {
  padding: 10px;
  margin-bottom: 10px;
  border: 2px solid #fcc;
  background-color: #ececec;
  display: inline-block;
}

#poller {
  display: block;
  cursor: pointer;
  border: 2px solid #ff0;
  background-color: #ffc;
  border: none;
  padding: 10px;
}

#poller:hover {
  background-color: #ffff88;
}

xhr.html

<div id="response">...</div>

<button id="poller">Poll</button>

xhr.js

function url(){
 return '/';
}

function poll(done){
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function(){
        if(xhr.readyState === 4 && xhr.status == 200 ){
            var foo = xhr.responseText;
            done(foo);
        }
    };
    xhr.open('get',url(),true);
    xhr.send(null);
}

var button = document.querySelector('#poller');
var response = document.querySelector('#response');

button.addEventListener('click', function(){
    response.innerText = '...';

    poll(function(data){
        button.innerText = 'Poll again';
        response.innerText = data.substr(0, 180) + '\n...';
    });
},false);