Firebase return [Object object] [duplicate]

I’m trying to get the value of a child that has been added to my database with cloud functions and then send this value with a push notification to my mobile app. The problem is that firebase instead of giving me the value of the child it gives me a [ObjectObject] and I can’t find the problem inside my code.

My index.js:

//import firebase functions modules
const functions = require('firebase-functions');
//import admin module
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);

exports.pushNotification = functions.database.ref('/users').onCreate((snapshot, context) => {

    //  Get the current value of what was written to the Realtime Database.
    const valueObject = snapshot.after.val();
    functions.logger.log("value is: " + valueObject);

    // Create a notification
    const payload = {
        notification: {
            title: "Value is: " + valueObject,
            body: "This is a test",
            sound: "default"
        }
    };

    //Create an options object that contains the time to live for the notification and the priority
    const options = {
        priority: "high",
        timeToLive: 60 * 60 * 24
    };

    return admin.messaging().sendToTopic("pushNotifications", payload, options);
});