### Run promises in series

Run an array of promises in series using `Array.reduce()` by creating a promise chain, where each promise returns the next promise when resolved.

```js
const series = ps => ps.reduce((p, next) => p.then(next), Promise.resolve());
// const delay = (d) => new Promise(r => setTimeout(r, d))
// series([() => delay(1000), () => delay(2000)]) -> executes each promise sequentially, taking a total of 3 seconds to complete
```