var config = {

  apiKey: "AIzaSyCvpYQu44zmRXA0XQkcxEuakyytRsnWXSc",

  authDomain: "stackoverflow.firebaseapp.com",

  databaseURL: "https://stackoverflow.firebaseio.com",

  projectId: "project-8080059325282098184",

  storageBucket: "project-8080059325282098184.appspot.com",

  messagingSenderId: "82293832823"

};

firebase.initializeApp(config);

//firebase.firestore.setLogLevel('debug');

​

var db = firebase.firestore();

var ref = db.collection("52230832").doc("test");

var variableObjectName = "favorites";

var qty = 3;

​

ref.set({

    name: "Frank",

    favorites: { food: "Pizza", quantity: Date.now() }

});

​

ref.onSnapshot(function(document) {

  console.log(document.data());

});

​

// Wait 5 seconds and then update the `abc-variable` field

setTimeout(function() {

  var name = "favorites";

  var update = {};

  update[name+".quantity"] = Date.now();

  ref.update(update);

}, 5000);