TypeError: firebase.storage is not a function

I faced the same problem. In my case, I needed to include storage module besides Firebase core.

import firebase from 'firebase/app';
import 'firebase/storage';  // <----

firebase.initializeApp({
  ...
});
const storageRef = firebase.storage().ref();

(npm firebase v5.0.4)

DEPRECATED, see below:

According to this answer, instead of firebase storage, in Node.js, google-cloud package storage should be used, and it seems that this answer should confirm it. Code example:

npm i --save google-cloud

Then:

const gcloud = require('google-cloud')

const storage = gcloud.storage({
    projectId: '<projectID>',
    keyFilename: 'service-account-credentials.json',
});

const bucket = storage.bucket('<projectID>.appspot.com')

As of 2018, this is the correct answer:

Or using only the storage part of the package:

npm install --save @google-cloud/storage

And then:

var storage = require('@google-cloud/storage')

Also check the docs for more.