CODEWITHSUNDEEP
javascriptfirebasefirebase-realtime-databasetransactionspromise
sixD
sixD

Reputation: 227

how to use the promise '.then' component of transaction in firebase

I'm using firebase and need to increment a counter so transaction seems to be the most appropriate contender. i understand that transaction uses a promise, however i am unclear (and the manuals dont have examples) on how to use the .then component of the promise.

At the moment in prototyping, i can 'slow it down' by using an alert like this:

var oldPosScore = firebase.database().ref('/data/n:'+stateNum[plus] + '/score/');
        oldPosScore.transaction (function(increment1) {
            alert ('POSITIVE statement number: ' + stateNum[plus] );            
            return ((increment1 || 0)*1 + 1);
        });

What syntax do i use to set this up? where/how does the .then work in this use-case?

EDIT (added data structure): Instead of firebase push keys i am using numbers so i can randomly select them.

enter image description here

Upvotes: 0

Views: 421

Answers (1)

MuruGan
MuruGan

Reputation: 1420

there you can use transaction promise like below,

var oldPosScore = firebase.database().ref('/data/n:'+stateNum[plus]);

    oldPosScore.child('score').transaction (function(increment1) {  
        return ((increment1 || 0)*1 + 1);
    }).then(function(){
      alert("transaction successfull");
}).catch(function(err){
   alert(err);
});

see my Js Fiddle Sample for Transaction "then" Promise

I have edited my Js fiddle. See this whether it works for you or not?

Upvotes: 1

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