30-seconds-of-code/javascript/snippets/run-promises-in-series.md

title, type, tags, cover, dateModified

title	type	tags	cover	dateModified
Run promises in series	snippet	function promise	sail-away	2020-10-22T20:24:30+03:00

Runs an array of promises in series.

• Use Array.prototype.reduce() to create a promise chain, where each promise returns the next promise when resolved.

const runPromisesInSeries = ps =>
  ps.reduce((p, next) => p.then(next), Promise.resolve());

const delay = d => new Promise(r => setTimeout(r, d));
runPromisesInSeries([() => delay(1000), () => delay(2000)]);
// Executes each promise sequentially, taking a total of 3 seconds to complete