This template shows how to keep the number of child nodes in a Firebase database below a given number. This can be used to limit the number of lines of a chat history or logs.

See file functions/index.js for the code.

The dependencies are listed in functions/package.json.

As an example we'll be using a simple chat database structure:

/functions-project-12345
    /chat
        /key-123456
            user: "Mat",
            text: "Hey Bob!"
        /key-123457
            user: "Bob",
            text: "Hey Mat! What's Up?"

Every time a new chat message is added the Function runs. It counts the number of chat messages and removes the old ones if there are too many.