Implement forEach

You are required to implement Array.prototype.forEach method, which calls the given callback function for each element in a given array.

Example:

const arr = [1, 2, 3];
arr.forEach((item) => {
  console.log(item);
});
// Output: 1, 2, 3

Solution

Let's just iterate over a given array, and for every item, call the given callback function.

Array.prototype.myForEach = function (cb) {
  for (let i = 0; i < this.length; i++) {
    cb(this[i], i, this);
  }
};

const arr = [1, 2, 3, 4, 5];
arr.myForEach((item) => {
  console.log(item); // 1, 2, 3, 4, 5
});

• Time complexity: O(N)
• Space complexity: O(1)