Demonstrating how Array.prototype.forEach(...) works by using it on Objects

forEachObject.js

Object.prototype["0"] = "test0";
let obj = {"1": "test1", "2": "test2"};

for (let k in obj) console.log(k); // 1, 2, 0

Object.defineProperty(obj, 'length', {
  value: 3,
  enumerable: false,
  writable: true,
  configurable: false
});

Array.prototype.forEach.call(obj, i => {console.log(i)}) // test0, test1, test2