David Dal Busco

How To Download A File With Node.js

If you ever need to download a file with Node.js, here is a small script to achieve your goal.

Feb 10, 2021

#javascript #nodejs #webdev

Photo by Savannah Wakefield on Unsplash

Over the weekend I made a dependency update of my time tracking app “Tie Tracker” (PWA / GitHub).

In this particular tool, I defer the heavy work to Web Workers so that the UI does not find itself in a blocking state.

Because the app is meant to work offline and, is available in the App Store and Google Play, I did not import the required workers’ dependencies through a CDN but, locally.

The app itself is developed with React but, I implemented the workers with vanilla JavaScript and no package manager to handle their dependencies.

Therefore, I had to come with a solution to update the libs with aNode.js script 😇.

Node Fetch

There is no window.fetch like API in Node.js but, there is a light-weight module that brings such capabilities. That’s why I used node-fetch to implement the download of the file.

npm i node-fetch --save-dev

Script

The script I developed to update my dependencies is the following:

const { createWriteStream } = require("fs");
const { pipeline } = require("stream");
const { promisify } = require("util");
const fetch = require("node-fetch");

const download = async ({ url, path }) => {
    const streamPipeline = promisify(pipeline);

    const response = await fetch(url);

    if (!response.ok) {
        throw new Error(`unexpected response ${response.statusText}`);
    }

    await streamPipeline(response.body, createWriteStream(path));
};

(async () => {
    try {
        await download({
            url: "https://unpkg.com/...@latest/....min.js",
            path: "./public/workers/libs/....min.js"
        });
    } catch (err) {
        console.error(err);
    }
})();

The above download function uses a stream pipeline to download a file, as displayed in the node-fetch README, and the built-in fs module to write the output to the file system.

Top Level Await is available as of Node.js v14.8.0 but, I used an immediate function because I integrated it in a chain in which it was not available yet.

That’s it 🥳

Continue Reading

If you want to read more about React and Web Workers, I published back to back three blog posts about it last year 😉.

To infinity and beyond!

David