Scan and lodash

scan-lodash.js

/*
This will turn your arrays into a keyed object like:
{
  1: <Obj 1>,
  2: <Obj 2>,
  3: <Obj 3>
}
Newest values will over-write old values.
*/
const keyedSource = source.scan((acc, arr) => _.assign(acc, _.keyby(arr, 'id'));

/*
This will take that keyed object and map it to an array like:
[<Obj 1>, <Obj 2>, <Obj 3>]
*/
const backToArray = keyedSource.map(_.values);