Falling Stars: find one-hit wonders on Spotify
During this summer I got bored from my Spotify playlist and started hunting new songs, the task revealed harder than I thought and I end up coding a small website to achieve my goal.
Falling Stars helps you find one-hit-wonders and create a Spotify playlist out of those songs.
The most interesting part, apart from discovering the nice Spotify API was having to deal with an asynchronous loop; I had basically to loop over the Related Artists of a song and search if one of them is a one-hit-wonder. If not start again with the Related Artists of the first of the previous ones.
To implement the loop I decided to use Promises. Promises are a new way to deal with asynchronous operation without using callbacks. Basically a Promise is an object with a state that changes when the associated asynchronous operation succeed or fails. A Promise can store functions that needs to be executed when the asynchronous operation completes and, best of all, promises can be chained.
Here’s how I ended up with the loop:
run: function(){
var self = this;
if( self.queue.length > 0 && self.playlist.length < self.limit ){
self.parsed.unshift(self.queue.shift());
self.parse(self.parsed[0])
.then(self.populate.bind(self))
.then(self.run.bind(self));
}else{
var playlist_name = 'Falling Stars - ' + new Date();
self.api('POST','/users/' + self.userId + '/playlists', {
name: playlist_name,
public: false
}).then(function(result){
self.api('POST','/users/' + self.userId + '/playlists/' + result.id + '/tracks',
self.playlist.map(function(track){
return track.uri;
})
).then(function(){
self.message('playlist', playlist_name);
});
});
}
}
The rest of the code is available on github and the project is online here: http://fallingstars-sandropaganotti.rhcloud.com/