I used the Web API Spotify. I followed the tutorial ( https://developer.spotify.com/web-api/tutorial/ ) to create authentication. However, it using Node.js and I wonder if we can do without it? (the rest of my code is in JavaScript and does not require Node.js)
You can work with Spotify's Web API using only frontend code.
You might want to have a look at the JavaScript wrapper as it offers language bindings for all API endpoints so it should save you a lot of time. If you're working without a backend, the only way to retrieve access tokens is through the Implicit Grant flow, see documentation or demo application for more detailed information.