This script runs on Node.js. On its website you can find instructions on how to install it. You can also follow this gist for a quick and easy way to install Node.js and npm.
Once installed, clone this repository and install its dependencies running:
$ npm install
You will need to register your app and get your own credentials from the Spotify for Developers Dashboard.
To do so, go to your Spotify for Developers Dashboard and create your application. You will also need to register this Redirect URI in your dashboard:
Once you have created your app, create .client_id.js and .client_secret.js files in the main directory and fill the files with your Spotify app's client_id and client_secret like:
module.exports = CLIENT_ID_OR_SECRET_GOES_HEREIn the main directory, run:
$ node app.js
Then, open http://localhost:8888 in a browser. Once you authorize your app to access your account, your library will be written to tracks.json in the main directory.