flat() / flatMap()
method
ES2019
flat() flattens nested arrays; flatMap() maps then flattens one level.
Syntax
array.flat(depth) array.flatMap(callback)
Example
javascript
const nested = [1, [2, 3], [4, [5, 6]]];
console.log(nested.flat()); // [1, 2, 3, 4, [5, 6]]
console.log(nested.flat(2)); // [1, 2, 3, 4, 5, 6]
console.log(nested.flat(Infinity)); // fully flattened
const sentences = ['Hello World', 'Foo Bar'];
const words = sentences.flatMap(s => s.split(' '));
console.log(words); // ['Hello', 'World', 'Foo', 'Bar']