Array Flat Polyfill with Depth Implementation

polyfill_for_array_flat.js

Array.prototype.myFlat = function (depth) {
  function getFlattenedArr(arr) {
    let res = [];
    let isSpreaded = false;
    for (let value of arr) {
      if (Array.isArray(value)) {
        isSpreaded = true;
        res.push(...value);
      } else {
        res.push(value);
      }
    }
    return {
      res,
      isSpreaded,
    };
  }

  let result = [...this];
  let counter = 0;
  while (counter < depth) {
    const { res, isSpreaded } = getFlattenedArr(result);
    result = res;
    counter++;
    if (!isSpreaded) break;
  }
  return result;
};

const arr = [[1, 2, 3], 4, [5, [6]], 7];
console.log(arr.myFlat(Infinity)); // [1,2,3,4,5,6,7];