Firebase transaction in nodeJs

What I try to achieve is simply increase a value in the database with a transaction. This is working for me as intended, but I always get following error in my firebase console:

Function returned undefined, expected Promise or value


My current call is as following:

exports.reportCounter = functions.database.ref('/user/{userId}/reports/{initiatorId}').onWrite((change,context) => {
const userId = context.params.userId;

return userRef.child(userId).child("numReports").transaction(function(numReports) {
return change.after.exists()?((numReports || 0) + 1):(numReports - 1);
})
});


I also tried returning the promise directly:

return userRef.child(userId).child("numToIncrement").transaction(function(numToIncrement) {
return ((numToIncrement || 0) + 1);
});


In both cases, the code is doing what it is supposed to do, but I still receive said error.

1 Answer
1

This is how you should implement the transaction, this way the function always returns a promise:

exports.reportCounter = functions.database.ref('/user/{userId}/reports/{initiatorId}').onWrite((change, context) => {
const userId = context.params.userId;
let increment;
if (change.after.exists() && !change.before.exists()) {
increment = 1;
} else if (!change.after.exists() && change.before.exists()) {
increment = -1;
}
return userRef.child(userId).child("numReports").transaction(function(numReports) {
return (numReports || 0) + increment;
})
});


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