Node.js: Unzip Async Await

Unzip a .zip file in an asynchronous Node.js context.

Photo by Florian Steciuk on Unsplash

I am developing a new feature of DeckDeckGo for which I have to unzip a data in Firebase Functions.

It took more time than expected to code such a Node.js function, that’s why I am sharing this solution, hoping it might help you some day too 😇.

Unzipper

Node.js provides a compression module Zlib but, it does not support ZIP files. Luckily, we can use the library unzipper to handle these.

npm i unzipper --save

Unzip With Async Await

My new feature reads and writes data uploaded in Firebase Storage through streams. I also develop my code with a promises (async / await) approach. Therefore, both have to coexist.

To narrow down the following example, I replaced the cloud storage with local files handled with file system streams (fs ).

The function unzip instantiates a stream on the zip data which is piped with unzipper . Each entry are iterated and piped themselves to writable outputs. Summarized: the zip is opened and each files it contains are extracted.

unzip is called in a retro compatible top await function and, that’s basically it 🥳.

const {Parse} = require('unzipper');
const {createWriteStream, createReadStream} = require('fs');

const unzip = () => {
  const stream = 
    createReadStream('/Users/david/data.zip').pipe(Parse());

  return new Promise((resolve, reject) => {
    stream.on('entry', (entry) => {
      const writeStream = 
        createWriteStream(`/Users/david/${entry.path}`);
      return entry.pipe(writeStream);
    });
    stream.on('finish', () => resolve());
    stream.on('error', (error) => reject(error));
  });
};

(async () => {
  try {
    await unzip();
  } catch (err) {
    console.error(err);
  }
})();

Read To String With Async Await

I had to read files with streams too. Consequently and cherry on top, here is how I integrated these in my code.

const {createReadStream} = require('fs');

const read = () => {
  const stream = 
    createReadStream('/Users/david/meta.json');

  return new…