title: Error when validating firebase token: `TypeError: firebase.auth(...).verifyIdToken is not a function`
body: <p>I am trying to verify id tokens generated on the front end in my nodejs app. I am following <a href="https://firebase.google.com/docs/auth/server/verify-id-tokens" rel="nofollow">this</a> guide.</p>
  
  <p>The token is generated fine. I save it as a cookie. I can print it to the nodejs console. When I try to validate it, I get this error:</p>
  
  <pre><code>TypeError: firebase.auth(...).verifyIdToken is not a function
      at router.get (/home/marcel/code/clairitech/website/routes/index.js:30:21)
      at Layer.handle [as handle_request] (/home/marcel/code/clairitech/website/node_modules/express/lib/router/layer.js:95:5)
      at next (/home/marcel/code/clairitech/website/node_modules/express/lib/router/route.js:131:13)
      at Route.dispatch (/home/marcel/code/clairitech/website/node_modules/express/lib/router/route.js:112:3)
      at Layer.handle [as handle_request] (/home/marcel/code/clairitech/website/node_modules/express/lib/router/layer.js:95:5)
      at /home/marcel/code/clairitech/website/node_modules/express/lib/router/index.js:277:22
      at Function.process_params (/home/marcel/code/clairitech/website/node_modules/express/lib/router/index.js:330:12)
      at next (/home/marcel/code/clairitech/website/node_modules/express/lib/router/index.js:271:10)
      at Function.handle (/home/marcel/code/clairitech/website/node_modules/express/lib/router/index.js:176:3)
      at router (/home/marcel/code/clairitech/website/node_modules/express/lib/router/index.js:46:12)
  </code></pre>
  
  <p>Here is my code:</p>
  
  <pre><code>const firebase = require('firebase').initializeApp({
    apiKey: "AIzaSyDLT76jVp0F2_fqbvV8azRz3HybD-****",
    authDomain: "****.firebaseapp.com",
    databaseURL: "https://****.firebaseio.com",
    storageBucket: "****.appspot.com",
    messagingSenderId: "******"
  }, 'admin')
  router.get('/', (req, res) =&gt; {
      firebase.auth().verifyIdToken(req.cookies.firebase_token).then(token =&gt; {
        console.log('token:')
        console.log(token)
      }).catch(err =&gt; { throw err })
  })
  </code></pre>
  
  <p>I am using firebase 3.4.1 from npm and node version 6.2.2.</p>
  
  <p>Edit 1: Added firebase config.</p>