Polyfill of Array.map

Array.prototype.mapPolyfill = function (condition) {
  const output = [];
  this.forEach((item, index) => {
    output[index] = condition(item, index, this);
  });
  return output;
};

const ans = [1, 2, 3, 4, 5].mapPolyfill((item) => item * 2);
console.log(ans);

// Output:
[2, 4, 6, 8, 10];