parallel.js

(function () {
	var c = Date.now();
	console.log('start: ' + c);
	new Promise(
		function (res, rej) {
			setTimeout(function (){
				console.log('1st fullfilled at ' + Date.now());
				res(1);
			}, 1000);
		}
	).then(
		function (res) {
			console.log('2nd then with ', arguments);
			return new Promise(
				function (_res, _rej){
					setTimeout(function (){
						console.log('2nd fullfilled at ' + Date.now());
						_res(2);
					}, 1000);
				}
			);
		}
	).then(
		function (res) {
			console.log('3rd then with ', arguments);
			console.log(Date.now() - c);
		}
	)
})();

serial.js

(function () {
	var c = Date.now();
	Promise.all([
		new Promise(function (res) {setTimeout(function () {res(3000);}, 3000);}),
		new Promise(function (res) {setTimeout(function () {res(2000);}, 2000);}),
		new Promise(function (res) {setTimeout(function () {res(1000);}, 1000);})
	]).then(
		function () {
			console.log('THEN: ' + (Date.now() - c));
			console.log(arguments);
		}
	)
})();

wrong-parellel.js

(function () {
	var c = Date.now();
	console.log('start: ' + c);
	new Promise(
		function (res, rej) {
			setTimeout(function (){
				console.log('1st fullfilled at ' + Date.now());
				res(1);
			}, 1000);
		}
	).then(
		function (res, rej) {
			console.log('2nd then with ', arguments);
			new Promise(
				function (_res, _rej){
					setTimeout(function (){
						console.log('2nd fullfilled at ' + Date.now());
						_res(2);
					}, 1000);
				}
			);
		}
	).then(
		function (res, rej) {
			console.log('3rd then with ', arguments);
			console.log(Date.now() - c);
		}
	)
})();