Cloud functions with firebase: firebase.functions is not a function

Question

After creating a cloud function addMessage on Firebase using Firebase SDK 4.12.0, the following code does not work when attempting to call the addMessage function from within my client app:

var firebase = require("../node_modules/firebase")
var functions = firebase.functions();

functions.httpsCallable("addMessage").call(
    //...
)

TypeError: firebase.functions is not a function

Answer 1

The solution was to add require("firebase/functions")