title: Firebase authentication, firebase is not defined
body: <p>Im trying to make a login page to my firebase project, but always when i send the params to the functions its returns "Firebase is not defined . Here's my code:</p>
  
  <pre><code>&lt;button id="login" onclick="signIn()"&gt;&lt;Login&lt;/button&gt;
  </code></pre>
  
  <p>The function signIn() only change the href to <a href="http://localhost:5000/signin/:email/:password" rel="nofollow noreferrer">http://localhost:5000/signin/:email/:password</a></p>
  
  <p>then i have this</p>
  
  <pre><code>const functions = require('firebase-functions');
  const adm = require('firebase-admin');
  const express = require('express');
  const signin = require('./modules/signin');
  const firebase = require("firebase");
  
  // // Create and Deploy Your First Cloud Functions
  adm.initializeApp(
      functions.config().adm
  );
  
  const app = express();
  
  app.get('/signin/:email/:password', (request, response) =&gt; {
      exports.signin = signin(request.params.email, request.params.password);    
  });
  
  exports.app = functions.https.onRequest(app);
  </code></pre>
  
  <p>and my function is only</p>
  
  <pre><code>function signin (email, password) {
  firebase.auth().signInWithEmailAndPassword(email, password).then(function(user) {
      // user signed in
      console.log ("Usuário logado com sucesso!");
      return True;
      }).catch(function(error) {
          var errorCode = error.code;
          var errorMessage = error.message;
  
          if (errorCode === 'auth/wrong-password') {
              // alert('Wrong password.');
              return false;
          } else {
              alert(errorCode+": "+errorMessage); 
              return false;        
          }
      });
  
  }
  
  module.exports = signin;
  </code></pre>
  
  <p>im trying to use the index.js on functions folder as a type of "controller" to call functions on backend, but im having trouble to solve this simple problem.</p>