How to add data to Firebase without replacing using NodeJS?

Question

I am trying to send a time difference between two distances from my NodeJS server to Firebase database.

function sendDatabase(dbName, payload1) {
    var timeNow = getTime();
    console.log(timeNow);
    var ref = db.ref(dbName);
    ref.set({difference:payload1});
}

dBName = IpBBEfCob0c1GaYkvAzog9rVdKn1/

payload1 is the time difference that I want to send.

dbName is a child node in the database and I want to save payload1 as child node of dbName every single time it executes.

But every time this function executes it will just replace it and no new entry will be created. I know that this is because the property name difference is the same every time, therefore I searched on Google to see if I can make it unique so that it will not replace, but I could not find a proper answer to my issue.

I am a beginner to Firebase and help with this would be much appreciated.

Have you tried push()? firebase.google.com/docs/reference/js/… — James Poag
– James Poag, Commented May 30, 2017 at 12:15
yes i tried push. But then it creates a unique ID node and saves just one instance under it. The next time it will create another node and save. What i want is to have everything in the same node — Vihanga Bandara
– Vihanga Bandara, Commented May 30, 2017 at 12:17
yes that is exactly what i want. but it shud be under the same dbName node — Vihanga Bandara
– Vihanga Bandara, Commented May 30, 2017 at 12:18
Instead, grab a reference to the difference node and push() children into it. push is chronologically ordered, so the unique key nodes will appear in order and you can filter by LimitToLast(2) to grab the last 2 nodes. — James Poag
– James Poag, Commented May 30, 2017 at 12:21

James Poag · Accepted Answer · 2017-05-30 12:31:56Z

3

You can't have multiple instances of the same key. Then it's not a key anymore. You can't do this:

dbName
 - difference : 00
 - difference : 01
 - difference : 02
 - difference : ...

What you can do is have multiple children of difference:

dbName
  + difference
    - khghjgfvhgfh : 00
    - khghjgfvhgfi : 01
    - khghjgfvhgfj : 02
    - khghjgfvhgfk : ...

By pushing unique children:

db.ref(dbName).child("difference").push(payload1)

push automatically orders children chronologically.

And when you query your nodes, LimitToLast, First, etc...

db.ref(dbName).child("difference").limitToLast(2)

answered May 30, 2017 at 12:31

James Poag

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