promise

with_promise.js

var promise = function(url) {
	return new Promise(function (resolve, reject) {
		var req = new XMLHttpRequest();
		req.open('GET', url);
		req.onload = function () {
			if (req.status == 200) {
				resolve(req.response);
			} else {
				reject(Error(req.statusText));
			}
		};
		req.onerror = function () {
			reject(Error("Nettwork Error"))
		};
		req.send();
	});
}
promise('http://localhost:3000/posts').then(function(result){
	var res = document.querySelector('#result')
	var fragment = document.createDocumentFragment();
	JSON.parse(result).slice().forEach(function(ele, i){
		var li = document.createElement('li');
		li.textContent += ele.comments;
		fragment.appendChild(li);
	});
	res.appendChild(fragment);
}, function(reject){
	console.log(reject);
}).catch(function(error){
	console.log(error);
})