JavaScript Array in essential

MyArray.js

function MyArray() {
  this._index = 0;
}

MyArray.prototype.push = function(v) {
  this[this._index++] = v;
} 

var arr = new MyArray();

arr.push(1);
arr.push(2);

// 1
console.log(arr[0])

// 2
console.log(arr[1]);