Promise waitAndCatch

01-promise-wait-and-catch.js

/**
 * Wait for a specified number of milliseconds. If a promise hasn't resolved, reject it.
 * This is a necessary replacement in some cases since cancellable promises aren't a thing
 * and is helpful if you want to wait _no longer than_ a specified amount of time.
 * @param {int} time Amount of time to wait before resolving arbitrarily.
 * @param {function} fn That returns a Promise. It will be run one tick before the timer starts.
 * @return {Promise}
 */
export function waitAndCatch(time, fn) {
  return new Promise((resolve, reject) => {
    fn().then(resolve).catch(reject);
    delay(time).then(reject);
  });
}

// Creates a new promise that automatically resolves after some timeout
export function delay(time) {
  return new Promise((resolve, reject) => {
    setTimeout(resolve, time);
  });
}

02-example.js

import { delay, waitAndCatch } from 'promise-wait-and-catch';

// mock something that takes some time
function doSomethingThatTakesAWhile() {
  // a more useful example would be calling an API, but in this case we'll just arbitrarily
  // run a 3000 millisecond task.
  return delay(3000);
}

waitAndCatch(2000, doSomethingThatTakesAWhile)
  .then(() => {
    console.log('Finished in time.');
  })
  .catch(() => {
    console.log('Took too long!');
  });

You should see "Took too long!" in the console. If you decrease the time doSomethingThatTakesAWhile takes to run to under 2000ms, you will see "Finished in time."