CODEWITHSUNDEEP
javascriptfirebasefirebase-realtime-databasefirebase-cloud-messaginggoogle-cloud-functions
Bitten Tech
Bitten Tech

Reputation: 145

TypeError: Cannot Read Property child of undefined

I am trying to make a node.js firebase function to send a notification to the user each time a node is added or updated inside the 'Notifications' parent node in my realtime database.

Here is my index.js-

let functions = require('firebase-functions');

let admin = require('firebase-admin');

admin.initializeApp();

exports.sendNotification = functions.database.ref('/Notifications/{postId}').onWrite((change, context) => {

//get the userId of the person receiving the notification because we need to get their token
 const receiverId = change.after.data.child('receiver_token').val();
 console.log("receiverId: ", receiverId);



 //get the message
 const message = change.after.data.child('content').val();
 console.log("message: ", message);



  const token = receiver_token;

  console.log("Construction the notification message.");
  const payload = {
    data: {
      data_type: "direct_message",
      title: "Open Up",
      message: message,

    }
  };

  return admin.messaging().sendToDevice(token, payload);
});

But everytime the error comes as it says the result of change.after.data is undefined. What is the problem. How do I fix it?

My Realtime Database structure:

enter image description here

Upvotes: 4

Views: 4023

Answers (1)

Peter Haddad
Peter Haddad

Reputation: 80934

Change this:

const receiverId = change.after.data.child('receiver_token').val();
console.log("receiverId: ", receiverId);
//get the message
const message = change.after.data.child('content').val();
console.log("message: ", message);

into this:

const receiverId = change.after.child('receiver_token').val();
console.log("receiverId: ", receiverId);
//get the message
const message = change.after.child('content').val();
console.log("message: ", message);

Both onWrite and onUpdate have the change parameter which has before and after fields. Each of these is a DataSnapshot with the same methods available in admin.database.DataSnapshot

admin.database.DataSnapshot does not contain a field called data that is why you get undefined error.

Upvotes: 4

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