patmigliaccio.com/async-fishing 12/11/16

async-fishing-xhr.js

function xhr({method = 'GET', url, async = true, responseType = ''}){
	let req = new XMLHttpRequest();
	req.open(method, url, async);
	req.responseType = responseType;

	let p = new Promise((resolve, reject) => {
		req.onreadystatechange = () => {
			if (req.readyState == XMLHttpRequest.DONE){
				if (200 <= req.status && req.status < 300){
					resolve(req.response);
				} else {
					reject(req.response);
				}
			}
		}
		
		req.send();
	});
	
	return p;
}