Array Train

Instead of using await Promise.all(array.map(async ...)) to fire all async functions at once, you can use await train(array, async ...) to run async functions sequentially, one after another — just like a train.

Installation

npm install array-train

Usage

Use train when you need to process items in series rather than in parallel.

import { train } from "array-train";

const responses = await train(
  [
    "https://www.google.com",
    "https://developer.mozilla.org",
    "https://github.com",
    // ...
  ],
  async (uri) => await fetch(uri)
);

Extra

Array Train provides three types of train functions:

Simple Train

import { simpleTrain } from "array-train";

await simpleTrain([1, 2, 3], async (x) => x + 1);

This works like the map function, returning [2, 3, 4]. It is also the default implementation of train.

Multiply Train

import { multiplyTrain } from "array-train";

await multiplyTrain([1, 2, 3], async (x) => [x, x + 1]);

This is an async version of flatMap, returning [1, 2, 2, 3, 3, 4].

Infinite Train

import { infiniteTrain } from "array-train";

await infiniteTrain([1, 2, 3], async (x) => ({
  output: [x * 10, x * 100],
  next: x < 3 ? [x + 1, x + 2] : [],
}));

This function continues processing as long as you provide next values, accumulating all output results.

License

MIT