delay.js

const delay = (ms, token = null) => new Promise((resolve, reject) => {
  const cancelled = () => reject({ cancelled: true });

  if (token && token.cancelled) {
    return cancelled();
  }
  
  const timeout = setTimeout(() => {
    if (!token || !token.cancelled) {
      resolve();
    } else {
      cancelled();
    }
  }, ms);
  
  if (token) {
    token.onCancel = () => {
      clearTimeout(timeout);
      cancelled();
    };
  }
});

class CancelToken {
  cancelled = false;

  cancel () {
    this.cancelled = true;
    this.onCancel();
  }

  onCancel () {
    //
  }
}

// Usage
const token = new CancelToken();

delay(2000, token)
  .then(() => {
    console.log('2 seconds passed!');
  })
  .catch(({ cancelled }) => {
    if (cancelled) {
      console.log('cancelled!');
    }
  });

if (Math.random() < 0.5) {
  token.can