Array Flat (array.flat())

array_flat.js

var arr1 = [1, 2, [3, 4]];
console.log(arr1.flat());
// [1, 2, 3, 4]

var arr2 = [1, 2, [3, 4, [5, 6]]];
console.log(arr2.flat()); // Default Level : 1
// [1, 2, 3, 4, [5, 6]]

var arr3 = [1, 2, [3, 4, [5, 6]]];
console.log(arr3.flat(2)); // Explicitly specified level : 2
// [1, 2, 3, 4, 5, 6]

var arr4 = [1, 2, [3, 4, [5, 6, [7, 8, [9, 10]]]]];
console.log(arr4.flat(Infinity));
// [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

var arr5 = [1, 2, , 4, 5];
console.log(arr5.flat());
// [1, 2, 4, 5]