Add child with automatically incremented custom ID - Firebase

Question

I want to add a new user to firebase database with auto increment id as shown below screenshots:

I have tried:

    var rootRef = firebase.database().ref();
    var storesRef = rootRef.child("/users");
    storesRef.set({
      "name": "user1",
      "pageId": "user1"
    });

Do you need the user ids to be `0,1,2,...`? Otherwise, you could use Firebases built-in ID generation, which also preserves the order of creation, because it takes the time of creation into account. — alex kucksdorf, Dec 05 '17 at 11:48
@alexkucksdorf yes, user id needed. Because I have imported from quickblox — Gajjar Tejas, Dec 05 '17 at 11:50
As Alex said: using sequentially, monotonously incrementing IDs like that is going to be a serious hinder to both the scalability and the offline behavior of your app. I recommend you read the Firebase blog post on this: https://firebase.googleblog.com/2014/04/best-practices-arrays-in-firebase.html — Frank van Puffelen, Dec 05 '17 at 15:31

alex kucksdorf · Answer 1 · 2017-12-05T16:03:46.357

I do not recommend this, but you can try the following:

storesRef.limitToLast(1).once('value', (snapshot) => {
    const nextID = parseInt(snapshot.key) + 1;
    let updates = {};
    updates['/users/' + nextID] = // your user;
    rootRef.update(updates);
});

However, I would strongly suggest you use Firebases automatically generated IDs instead, since this approach is very error prone.

You should also have a look at this answer.

score 0 · Answer 2 · answered Mar 30 '18 at 14:36

I spent a long-ish time trying to solve this problem for my own project and as usual it turned out to be deceptively easy:

var newUserIndex;

storesRef.on('value', snap =>{
  newUserIndex = snap.val().length;    
});

database.ref('users/' + newUserIndex).set({name:'user1', pageId:'user1'});

Because the database is zero-based, snap.val().length always gives the next index needed. I thought using snap may be overkill for this and a waste of resources (I've only just started using Firebase so still getting to grips with it) - but checking the usage stats in console, apparently not.

Not everyone is building an app that has multiple users and needs scalability. I understand the benefit of using auto generated keys using push() but it's not always the right solution for smaller projects and single user projects.

Add child with automatically incremented custom ID - Firebase

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