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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Top comments (1)
Thank you!