Implement map, filter, reduce, flat
Build your own map
Build your own filter
Build your own reduce
Build your own flat
Build your own forEach
Build your own find
Build your own findIndex
Build your own some
Build your own every
Build your own includes
Build your own indexOf
Build your own flatMap
Build your own concat
Build your own slice
Build your own reverse (in-place)
Build your own join
Build your own fill