function add() {
  let args = [];
  for (let i = 0; i < arguments.length; i++) {
    args[i] = arguments[i];
  }
  return args.reduce((sum, value) => sum + value);
}

// function delay() {
//   let args = [];
//   for (let i = 0; i < arguments.length; i++) {
//     args[i] = arguments[i];
//   }
//   let callback = args.pop();
//   setTimeout(() => callback.apply(null, args), 2000);
// }
//
// delay(1, 2, 3, 4, 5, add);

function delayPromise() {
  let args = [];
  for (let i = 0; i < arguments.length; i++) {
    args[i] = arguments[i];
  }
  let callback = args.pop();
  return new Promise(resolve => {
    setTimeout(() => resolve(callback.apply(null, args), 2000));
  });
}

delayPromise(1, 2, 3, 4, 5, add).then(response => console.log(response));