Its my first attempt at both Angular and using Spotify's APIs. So its probably buggy. It also desperately needs UI / UX work. A link is provided to my public GitHub repo if you'd like to contribute, or even log bugs 🙂
I've tested the tool with 250+ songs and its able to import them in roughly 30 seconds. I suspect it will work with larger playlists. However, I'm not entirely sure what will happen since most processing is done in memory (in the browser). Also, I've only used Chrome, so please let me know how it runs on other browsers.
Last but not least, the tool requires that you grant it the ability to modify / create public playlists for your account ("playlist-modify-public" scope, for the techie folk).
Enjoy and ride those electro waves!