code: function sortObj(obj) {
      return Object.keys(obj).sort()
          .filter(key => obj[key] || obj[key] === 0)
          .reduce((acc, key) => ({ ...acc, [key]: obj[key] }), {});
  }
docs: ES6 uses the order we've inserted the strings http://exploringjs.com/es6/ch_oop-besides-classes.html#_traversal-order-of-properties