jsprint fiddle

HTML

<script src="http://brigand.github.io/jsprint/build/output/jsprint.min.js"></script>
<div id="a"></div>

JavaScript

function readyStateCallback () {
  jsprint(this.readyState);
};

var oReq = new XMLHttpRequest();
oReq.onreadystatechange = readyStateCallback;
oReq.open("get", "http://foobarbaz.nnn", true);
oReq.send();