JS: Listen to ajax calls from Javascript

ajaxListener.js

// override XMLHttpRequest
// source: https://gist.github.com/icodejs/3183154

var open = window.XMLHttpRequest.prototype.open,
    send = window.XMLHttpRequest.prototype.send;

function openReplacement(method, url, async, user, password) {
    return open.apply(this, arguments);
}

function sendReplacement(data) {
    this.addEventListener('readystatechange', function() { 
        // Catch response here
    }, false); 
    return send.apply(this, arguments);
}

window.XMLHttpRequest.prototype.open = openReplacement;
window.XMLHttpRequest.prototype.send = sendReplacement;