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

runPromisesInSeries

Runs an array of promises in series.

Use Array.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