Cancellable wait -- an ES6 promise example

cancellable-wait.js

const wait = (
  time,
  cancel = Promise.reject()
) => new Promise((resolve, reject) => {
  const timer = setTimeout(resolve, time);

  cancel.then(() => {
    clearTimeout(timer);
    reject(new Error('Cancelled'));
  });
});

const shouldCancel = Promise.resolve(); // Yes, cancel
// const shouldCancel = Promise.reject(); // No cancel

wait(2000, shouldCancel).then(
  () => console.log('Hello!'),
  (e) => console.log(e) // [Error: Cancelled]
);