Listen for Ajax Calls

To follow all ajax calls on an HTML document, you can overwrite the XMLHttpRequest prototype. This way, you can watch for actions on methods of XMLHttpRequest objects.

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

function openReplacement(method, url, async, user, password) {
    var syncMode = async !== false ? 'async' : 'sync';
    console.warn(
        'Preparing ' +
        syncMode +
        ' HTTP request : ' +
        method +
        ' ' +
        url
    );
    return open.apply(this, arguments);
}

function sendReplacement(data) {
    console.warn('Sending HTTP request data : ', data);

    if (this.onreadystatechange) {
        this._onreadystatechange = this.onreadystatechange;
    }
    this.onreadystatechange = onReadyStateChangeReplacement;

    return send.apply(this, arguments);
}

function onReadyStateChangeReplacement() {
    console.warn('HTTP request ready state changed : ' + this.readyState);
    if (this._onreadystatechange) {
        return this._onreadystatechange.apply(this, arguments);
    }
}

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