Array.js

class Array {
  constructor() {
    this.length = 0;
  }

  push(value) {
    this[this.length] = value;
    this.length++;
  }

  pop() {
    const value = this[this.length - 1];
    this.length--;
    return value;
  }

  forEach(fn) {
    // iterate over the array
      // invoke fn with each value in the array
  }
}

const arr = new Array();
arr.push(1);
console.log(arr.length);
arr.push(10);
console.log(arr.length);
console.log(arr[0]); // -> 1
console.log(arr[1]); // -> 10
console.log(arr.pop()); // -> 10
console.log(arr.length); // -> 1

arr.forEach((value, index, array) => {
  console.log(value, index, array);
});