Array FlatMap

FlatMap is a single method which can be usable for flat and map methods.

As you know flat(), flattening the 1-level deep and map() to loop into an array.

If we include both, we called flatMap()

So, instead if calling two methods flat() and map(), you can use single method called flatMap().

let plants = ['', '', '', ''];//  map + flatplants.map(plant => [plant, '']).flat();// Output//["", "", "", "", "", "", "", ""]//  flatMapplants.flatMap(plant => [plant, ""])// Output// ["", "", "", "", "", "", "", ""]

How flatMap() works?

FlatMap() always do first map() and then it flat().

In flat(), we use to pass arguments where you set the depth, arguments define how deep a nested array should be flattened.

let plants = [[["", ""]]];plants.flat(2);// ["", ""]

flatMap() do only 1 level deep flattening.

let plants = [[["", ""]]];plants.flatMap(plant => [plant]);// [["", ""]]

Filter using flatMap

Yes, You can also do filter here using flatMap().

let arr = [5, 4, -3, 20, -4, 18]arr.flatMap(i => {  return i < 0 ? [] : [i];})// [5, 4, 20, 18]

Reference

• MDN Docs of FlatMap

Summary

flatMap() method always helps if you want to use map and flat methods both together.

Thanks for reading the article