Intercept XMLHttpRequest and modify responseText

//
// firefox, ie8+ 
//
var accessor = Object.getOwnPropertyDescriptor(XMLHttpRequest.prototype, 'responseText');

Object.defineProperty(XMLHttpRequest.prototype, 'responseText', {
	get: function() {
		console.log('get responseText');
		return accessor.get.call(this);
	},
	set: function(str) {
		console.log('set responseText: %s', str);
		//return accessor.set.call(this, str);
	},
	configurable: true
});


//
// chrome, safari (accessor == null)
//
var rawOpen = XMLHttpRequest.prototype.open;

XMLHttpRequest.prototype.open = function() {
	if (!this._hooked) {
		this._hooked = true;
		setupHook(this);
	}
	rawOpen.apply(this, arguments);
}

function setupHook(xhr) {
	function getter() {
		console.log('get responseText');

		delete xhr.responseText;
		var ret = xhr.responseText;
		setup();
		return ret;
	}

	function setter(str) {
		console.log('set responseText: %s', str);
	}

	function setup() {
		Object.defineProperty(xhr, 'responseText', {
			get: getter,
			set: setter,
			configurable: true
		});
	}
	setup();
}