How do you un-deploy Cloud Functions for Firebase?

To delete a function explicitly use the following command:

$ firebase functions:delete myFunction

Replace myFunction with your function name. For detailed info. follow this link: https://firebase.google.com/docs/functions/manage-functions

Functions get deleted when they aren't present during a firebase deploy. Most commonly that'd be because because you removed the function from your index.js, but if you've removed the whole functions directory that'll work too.

To continue work on a function for which you don't have the source anymore, the easiest is to start fresh. The function(s) you deploy will replace the ones you deployed previously.

Alternatively, if you're partial to using the Google Cloud Console instead of the Firebase Console, the Cloud Console will show you the code for the currently-deployed function, so you can copy-paste it onto your local machine.

The Cloud Console also has a 'delete' button for every function, and even a web editor. Be aware when editing functions from the Cloud Console though: your next firebase deploy will overwrite any changes.