XMLHttpRequest under Promise

var pr = new Promise(function(resolve, reject) {
	var fn = function(event) {
		console.log("Event type: %s, Event target.readyState: %d, Event target.status: %d, Event target.statusText: %s", 
			event.type,
			event.target.readyState,
			event.target.status,
			event.target.statusText
		);

		if (event.type == "error" || event.type == "abort" || (event.type == "load" && (event.target.readyState != XMLHttpRequest.DONE || event.target.status != 200))) {
			reject("Very bad...");
		} else if (event.type == "load" && event.target.readyState == XMLHttpRequest.DONE && event.target.status == "200") {
			resolve("It's OK!");
		}
	}
	var req = new XMLHttpRequest();
	// https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequestEventTarget
	req.addEventListener("abort", fn);
	req.addEventListener("error", fn);
	req.addEventListener("load", fn);
	req.addEventListener("loadstart", fn);
	req.addEventListener("progress", fn);
	req.addEventListener("timeout", fn);
	req.addEventListener("loadend", fn);

	req.open("GET", "timeout.php");
	req.send();
});
pr.then(function() {
	console.log("resolved", arguments);
}, function() {
	console.log("rejected", arguments);
});

Example of asynchronous loading via XMLHttpRequest with Promise