Returns a copy of the collection with the remaining collections merged in,
calling the merger function whenever an existing value is encountered.
mergeWith<C>(merger: (oldVal: unknown, newVal: unknown, key: unknown) => unknown,
collection: C,
...collections: Array<Iterable<unknown> | Iterable<[unknown, unknown]> | {[key: string]: unknown}>): C
A functional alternative to collection.mergeWith() which will also work
with plain Objects and Arrays.
const { mergeWith } = require('immutable')
const original = { x: 123, y: 456 }
mergeWith(
(oldVal, newVal) => oldVal + newVal,
original,
{ y: 789, z: 'abc' }
) // { x: 123, y: 1245, z: 'abc' }
console.log(original) // { x: 123, y: 456 }run it