I finished my playlist recommendation app! First, a user can search for an artist they have in mind. When they click the search button, the app makes an ajax call to the Spotify API and returns the artists with the search query as their name and lists them all sorted by popularity. You can then click on the correct one which then adds their name to the list on the left. After you put in a few artists (you can put in up to 10) and click the Find Playlist button, my app looks through all of the playlists in the database but skips ones that only have less than 3 unique artists. It then calculates the similarity score and stores the playlists that have the good scores. It will then show you the five playlists that had the highest scores. You can click on the play button (I made that too!) and play a 30 second preview to see if you actually like the songs or not. Because in the database, I stored each song's url given in the Spotify's track object, it came in handy when I made this play button. It's actually using a Javascript object called Audio. I basically create a new Audio object using the constructor and each track's preview url and when you call .play() on it, it plays!
Here's what it looks like.
Here's what it looks like.