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I have two Firebase Cloud functions, one is written in "old" version, and one -- in "new":

exports.recountTotalCalories = functions.database.ref('/mealsOf/userId/day/meals/mealId')
 .onWrite(
 async( change ) => 
 const collectionRef= change.after.ref.parent;
 const counterRef= collectionRef.ref.parent.ref.child('totalCalories');
 let finalSum = await (collectionRef.ref.once('value').then( (snap) => 
 let sum= 0;
 snap.forEach( (child) => 
 console.log(child.val().numCalories);
 sum= sum+parseInt(child.val().numCalories);
 )
 return sum ;
 ));
 return await counterRef.set(finalSum);
 
 );

exports.updateColors = functions.database.ref('/mealsOf/userId/day/totalCalories')
.onWrite(
 async(change,context) => 
 const rootRef = change.after.ref.root.child('userInfo/'+context.params.userId);
 let calorieLimit = await rootRef.once('value').then( (snapshot) => 
 return snapshot.val();
 );
 let totalCalories = change.after.val();
 const collectionRef = change.after.ref.parent.ref.child('meals');
 return await collectionRef.ref.once('value').then ( (snapshot) => 
 snapshot.forEach( (child) => 
 console.log(totalCalories);
 console.log(calorieLimit);
 child.redZone = totalCalories > calorieLimit;
 console.log(child.redZone);
 );
 );
 
);

The first function works fine, it is the second that gives me trouble by saying "cannot read the property ref of undefined", which I found out by exploring the logs in Firebase console:

TypeError: Cannot read property 'ref' of undefined
 at exports.updateColors.functions.database.ref.onWrite (/srv/index.js:105:47)
 at cloudFunctionNewSignature (/srv/node_modules/firebase-functions/lib/cloud-functions.js:105:23)
 at /worker/worker.js:756:24
 at <anonymous>
 at process._tickDomainCallback (internal/

So, a certain SO thread firebase cloud functions Cannot read property 'ref' of undefined recommends "upgrading" Firebase cloud functions. But I am not sure just how. I have tried issuing the commands suggested here: Firebase functions: cannot read property 'user_id' of undefined on my machine (Windows 10), it seemed to have done some work, but the error persists on the Realtime Database. What am I missing?

EDIT: the log entry refers to line const collectionRef = change.after.ref.parent.child('meals');, and even more precisely -- to change.after.ref. But We are already accessing this in the beginning of the function, why does not it complain about it then?

EDIT': Here is my package.json file:

 "name": "functions",
 "description": "Cloud Functions for Firebase",
 "scripts": 
 "serve": "firebase serve --only functions",
 "shell": "firebase functions:shell",
 "start": "npm run shell",
 "deploy": "firebase deploy --only functions",
 "logs": "firebase functions:log"
 ,
 "dependencies": 
 "firebase-admin": "~6.0.0",
 "firebase-functions": "^2.1.0"
 ,
 "private": true,
 "engines": 
 "node": "8"
 

EDIT'': I re-wrote my second function using async (see the update above) and now it seems to execute all-right, except that the log is full of false promises and the desired change is not made to the database, anyway:

EDIT''': Now, this is the latest version of my second function, which finally does the trick:

exports.updateColors = functions.database.ref('/mealsOf/userId/day/totalCalories')
 .onWrite(
 async(change,context) => 
 const rootRef = change.after.ref.root.child('userInfo/'+context.params.userId);
 let calorieLimit = await rootRef.once('value').then( (snapshot) => 
 return snapshot.val();
 );
 let totalCalories = await change.after.ref.once('value').then((snap) => 
 return snap.val();
 );
 const collectionRef = change.after.ref.parent.ref.child('meals');
 return await collectionRef.ref.once('value').then ( (snapshot) => 
 snapshot.forEach( (child) => 
 console.log(totalCalories);
 console.log(calorieLimit);
 child.ref.child('redZone').ref.set(totalCalories > calorieLimit);
 console.log(child.val());
 );
 );
 
 );

Getting the hang of JavaScript is tricky, it seems.