Creating an async version of forEach on Array.prototype

asyncForEach.js

// extend the Array prototype with an asyncForEach method
Array.prototype.asyncForEach = async function (fn) {
  for (let i = 0; i < this.length; i++) {
    await fn(this[i], i);
  }
};

const arr = ['a', 'b', 'c', 'd'];

// define a Promise wrapper around the setTimeout function
function wait (fn, time) {
  return new Promise(resolve => setTimeout(() => {fn();resolve();}, time));
}

// call an asynchronous function upon each element in the array
arr.asyncForEach(async (item, index) => {
  await wait(() => console.log(item), 500);
});