The `flat()` method is used to flatten a multidimensional array. This means if, for example, you had a two-dimensional array, after running the flat() method on it, it will become a one-dimensional array with the entire nested elements all in the same row of that result array.
Array flat() Syntax:
Array flat() Method Parameters:
By default `flat()` method, flattens only one level and so arrays nested beyond one level don’t get flatten. But we can provide an optional `depth` argument to tell this method to do recursive flattening up to a given depth.
For example, if we set the argument to 1 that means one level depth (This is the default value). The value 2 means two level depth. Or we can set the value to `Infinity` to completely flatten the structure regardless of how deep it is.
Array flat() Method Return Value:
The method doesn’t change the original array and instead it’ll return a single-dimensional array with the values of the target multidimensional array all as its elements.
const arr = [ [1,2,3,4,5], [6,7,8,9], [ ['a','b','c'], ['d','e','f','g','h'] ] ]; const flatten = arr.flat(); const flatten2 = arr.flat(2); console.log(flatten); console.log(flatten2);
[1, 2, 3, 4, 5, 6, 7, 8, 9, ["a", "b", "c"], ["d", "e", "f", "g", "h"]] [1, 2, 3, 4, 5, 6, 7, 8, 9, "a", "b", "c", "d", "e", "f", "g", "h"]