Promise sequence - https://github.com/azu/promises-book/issues/46

promise-sequence-test.js

"use strict";
var assert = require("power-assert");
var sequence = require("../lib/promise-sequence").sequencePromises;
describe("promise-sequence", function () {
    it("should sequence promises", function () {
        var promisedIdentity = [1, 2, 4, 8, 16, 32].map(function (value) {
            return function identify() {
                return new Promise(function (resolve) {
                    setTimeout(function () {
                        resolve(value);
                    }, value);
                })
            }
        });
        var startDate = Date.now();
        return sequence(promisedIdentity).then(function (values) {
            console.log(Date.now() - startDate + "ms");// 約64ms
            assert.deepEqual(values, [1, 2, 4, 8, 16, 32]);
        });
    });
});

promise-sequence.js

"use strict";
function sequencePromises(promises) {
    var results = [];
    var pushResult = Array.prototype.push.bind(results);
    return promises.reduce(function (prevPromise, promisedIdentity) {
        return prevPromise.then(function () {
            return Promise.resolve(promisedIdentity()).then(pushResult);
        });
    }, Promise.resolve()).then(function () {
        return results;
    });
}

module.exports.sequencePromises = sequencePromises;