how to fix firebase function Unhandled error Error

Question

i am trying to fetch firebase database in functions but I can't figure out what's causing the error. here's my code

exports.test = functions.https.onCall(async (data, context) => {
console.log(data)
const sessionID = data.sessionID

const snapshot = await admin.database().ref('/test/'+sessionID).once('v‌alue');
 console.log(snapshot);
 return snapshot

})

this is how I am calling it from client side javascript

function callServer(){

    var signInCartIn = firebase.functions().httpsCallable('signInCartIn');

        var cartInfo = {
            "sessionID":"23234",
            "log":"6425",
            "cuso_id":"cus_IP83EOJ9843s",
            "pjo_id":"tm_1HoKt34xY1b"
        }

        signInCartIn(paymentInfo).then(function(result) {
          // Read result of the Cloud Function.

 
        }).catch(function(error) {
          // Getting the Error details.
          var code = error.code;
          var message = error.message;
          var details = error.details;

          console.log(message)
          // ...
        })

}

I keep getting this error when I call the function

Unhandled error Error: Query.once failed: First argument must be a valid event type = "value", "child_added", "child_removed", "child_changed", or "child_moved".

what is causing the error and how can I fix it?

You probably want to log and return snapshot.val() instead of snapshot (as snapshot itself isnot a JSON object). But that shouldn't be causing the error you get. The once() call looks fine to me. Are you sure that error is coming from this code? — Frank van Puffelen
– Frank van Puffelen, Commented Nov 20, 2020 at 0:43
@FrankvanPuffelen I thought so too. I have included the client side call to see maybe I'm missing something — e.iluf
– e.iluf, Commented Nov 20, 2020 at 1:28

Stratubas · Accepted Answer · 2020-11-21 19:13:46Z

2

What seems to be value is not really value.

There are hidden characters in there, a \u200c and a \u200b.

Looks like a nasty copy-paste. Delete it and type it yourself.

const yourValue = 'v‌alue';
const realValue = 'value';

const yourCharCodes = yourValue.split('').map(c => c.charCodeAt(0)).join(',');
const realCharCodes = realValue.split('').map(c => c.charCodeAt(0)).join(',');
console.log('yourCharCodes:', yourCharCodes);
console.log('realCharCodes:', realCharCodes);

edited Nov 21, 2020 at 19:13

answered Nov 20, 2020 at 1:29

Stratubas

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3 Comments

Frank van Puffelen Over a year ago

Great catch Stratubas. I wish I could upload multiple times. There are indeed two non-visible unicode characters in there (‌ and ).

e.iluf Over a year ago

where exactly are they located and were you able to find them?

Stratubas Over a year ago

@learner101 I don't have a specific method. I just tried copy-pasting your 'value' in Chrome dev console, to check for === with a "normal" 'value', and two red dots appeared in the text.

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