YOU CALL THIS IN JADE: firebase.initializeApp(config); IN THE BEGIN OF THE FUNC
script.
function signInWithGoogle() {
firebase.initializeApp(config);
var googleAuthProvider = new firebase.auth.GoogleAuthProvider
firebase.auth().signInWithPopup(googleAuthProvider)
.then(function (data){
console.log(data)
})
.catch(function(error){
console.log(error)
})
}