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(),…

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 + flat
plants.map(plant => [plant, '?']).flat();
// Output
//["?", "?", "?", "?", "?", "?", "?", "?"]

// ✅ flatMap
plants.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 ?



Summary ∑

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

Thanks for reading the article ❤️

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