Spotify on Glitch (node) keep login on refresh

I’m trying to create a very simple Spotify app with Glitch which adds the user’s currently playing song to a playlist.

A lot of the official Spotify apps on Glitch seem a bit … glitchy

For example, I want to remix this simple authorisation demo, which uses the node.js wrapper for the Spotify API – but every time I refresh the page it forgets that I have logged in and I have to authorise again (and you can see that behaviour if you log into the official auth demo I linked to).

Can anyone share an example (preferably with Spotify+Node.js!) where the login state is remembered after the browser is refreshed?