Bnaya

// You probobly don't need a helper library for Promise/Async after all

const seedValues = [Promise.resolve(777), Promise.resolve(888)];

// reduce
// Promise based
seedValues
  .reduce((accumulator, currentValue) =>
    accumulator.then(v => currentValue.then(cv => v + cv))
  )

Bnaya

(function () {
    'use strict';

    var duringErrorTrack = false;
    var ua = 'UA-XXXXXX-X'

    // don't break old browsers
    if (!window.addEventListener) {
        return;
    }