How to get data from wildcard in firebase cloud functions

Question

Assuming that I trigger events on the following ref(\'/users/{userId}/items/{newItem}\') I want to get a value from inside the wildcard userId

Answer 1

In firestore you can use this.

exports.getUser = functions.firestore
    .document('users/{userId}').onWrite((change, context) => {
        let userId = context.params.userId;
        //...
    });