30-seconds-of-code/snippets/chainAsync.md

title, tags, expertise, cover, firstSeen, lastUpdated

title	tags	expertise	cover	firstSeen	lastUpdated
Chain async functions	function	intermediate	blog_images/tram-car.jpg	2017-12-17T17:55:51+02:00	2020-09-15T16:28:04+03:00

Chains asynchronous functions.

• Loop through an array of functions containing asynchronous events, calling next when each asynchronous event has completed.

const chainAsync = fns => {
  let curr = 0;
  const last = fns[fns.length - 1];
  const next = () => {
    const fn = fns[curr++];
    fn === last ? fn() : fn(next);
  };
  next();
};

chainAsync([
  next => {
    console.log('0 seconds');
    setTimeout(next, 1000);
  },
  next => {
    console.log('1 second');
    setTimeout(next, 1000);
  },
  () => {
    console.log('2 second');
  }
]);