promise_all

var items = [1, 2, 3, 4, 5];
var fn = function asyncMultiplyBy2(v) { // sample async action
    return new Promise(resolve => setTimeout(() => resolve(v * 2), 100));
};
// map over forEach since it returns

var actions = items.map(fn); // run the function over all items.

// we now have a promises array and we want to wait for it

var results = Promise.all(actions); // pass array of promises

results.then(data => // or just .then(console.log)
    console.log(data) // [2, 4, 6, 8, 10]
);

// we can nest this of course, as I said, `then` chains:

var res2 = Promise.all([1, 2, 3, 4, 5].map(fn)).then(
    data => Promise.all(data.map(fn))
).then(function(data) {
    // the next `then` is executed after the promise returned from the previous
    // `then` fulfilled, in this case it's an aggregate promise because of 
    // the `.all` 
    return Promise.all(data.map(fn));
}).then(function(data) {
    // just for good measure
    return Promise.all(data.map(fn));
});

// now to get the results:

res2.then(function(data) {
    console.log(data); // [16, 32, 48, 64, 80]
});

/* Мой тест */
Promise.all(items.map(function(item) {
    return new Promise(function(resolve, reject) {
        return setTimeout(() => resolve(item + 2), 100);
    });
})).then(function(data) {
    console.log(data);
});