Firebase Cookbook

How to do it...

1. As a general use case, we can monitor any path or data we want using nothing but the changed() function, this will return a true value if the data did change. So, let's now learn how we can implement it:

      exports.updateStats =          functions.database.ref('/path/to/data').onWrite(         event => {         const data = event.data;         const anotherData = data.child('childPath');         if(anotherData.changed()) {              //TODO: implement notification          } else {              //return promise.         }      });

 It's as simple as that, we can check if our data changed.