How Do I Use Javascript Promise Chaining With Firebase Authentication And Firebase?

I need to utilize a key stored in my firebase using the user's firebase user id. The steps to my function are the following: 1) Get the Firebase User ID after authentication 2)

Solution 1:

You must use firebase.auth().onAuthStateChanged to get the uid bcs .auth.currentUser.uid will NOT be available on page load. It shows up a microsecond after (it's asynchronous).

To do what you want simply build out a promise function and call it within .onAuthStateChanged and .then do your other function. You custom promise might look like:

functionfetchUserData(){
    returnnewPromise(function(resolve, reject){
        var db = firebase.firestore(); // OR realtime db
        db.collection("users").get().then(function(snap) {
            resolve (snap);
        }).catch(function(error) {
            reject (error);
        });
    }); 
}

Within .onAuthStateChange just do something like:

fetchUserData().then((snap) => {
    // do your thing

})
.catch((error) => {
    console.log(error);
});