Exception "firebase.functions() takes ... no argument ..." when specifying a region for a Cloud Function

By trial and error I found that you have to do it like this:

var config = {
            apiKey: "xxxxxxxxxx",
            authDomain: "xxxxxxxxxx",
            databaseURL: "xxxxxxxxxx",
            projectId: "xxxxxxxxxx",
            storageBucket: "xxxxxxxxxx",
            messagingSenderId: "xxxxxxxxxx",
        };
var fireApp = firebase.initializeApp(config);
var functions = fireApp.functions('europe-west1');