javascript - Flatten n dimensional array without concat or reduce

Question

here I flattened a two dimensional array like the following

function flatArray(a, b) {

  return a.concat(b);

}

console.log([
  ['1', '2', '3'],
  ['4', '5', '6']
].reduce(flatArray));

Answer 1

A different approach, works in situ.

function flatten(array) {
    var l = array.length, temp;
    while (l--) {
        if (Array.isArray(array[l])) {
            flatten(array[l]);
            temp = array[l].slice();
            temp.unshift(1);
            temp.unshift(l);
            [].splice.apply(array, temp);
        }
    }
}


var array = [['1', '2', '3'], ['4', '5', ['6'], ['7', '8']]];

flatten(array);

console.log(array);