@unction/nestedApply

(MapperFunctionType<A, B> => Array | Set | Record<string | number | symbol, B> | Map<B, A> | string => Array | Set | Record<string | number | symbol, unknown> | Map<B, unknown> | string) => MapperFunctionType<A, B> => number => Array | Set | Record<string | number | symbol, B> | Map<B, A> | string => Array | Set | Record<string | number | symbol, B> | Map<B, A> | string

Takes a function (the application) that takes function(s) (later referred to as the inner) and value(s) (mapValues(), forEach(), selectValues()), a function (the inner) that will be applied to a value(s), and finally a number (depth) to apply that applicator around the inner.

In the below example we want to take two sets of records and index them by id:

const records = [
  [
    {
      id: "a1",
      type: "commercial",
    },
    {
      id: "a2",
      type: "commercial",
    }
  ],
  [
    {
      id: "b1",
      type: "residential",
    },
    {
      id: "b2",
      type: "residential",
    }
  ]
]

Normally we'd just do mapValues(indexBy(key("id"))), however we can make this easier and dynamic:

const nestedIndexById = nestedApply(mapValues)(indexBy(key("id")))(1)

nestedIndexById(records)

And the result:

[
  {
    a1: {
      id: "a1",
      type: "commercial",
    },
    a2: {
      id: "a2",
      type: "commercial",
    },
  },
  {
    b1: {
      id: "b1",
      type: "residential",
    },
    b2: {
      id: "b2",
      type: "residential",
    },
  },
]