Arrays & Array Methods (map, filter, reduce)

const arr = [1, [2, [3, 4], 5]];
const flattened = arr.flat(2);

Number of elements to flatten
Target array length
Depth of flattening
The argument in flat() specifies depth: 1) Controls how many levels deep to flatten, 2) flat(2) flattens up to 2 levels of nesting, 3) Default depth is 1 if no argument provided, 4) Infinity can be used for maximum depth, 5) Doesn't modify original array, 6) Removes empty slots in sparse arrays, 7) More convenient than recursive flattening, 8) Common for handling nested data structures.
Number of iterations