Develop Reference

window.onload starts before indexed db statements

Good afternoon all,
My issue is javascript related, I have made one function called checkflights, a series of statements to open an indexeddb database and one window.onload that triggers checkflights.
It seems that the window.onload triggers before the open database statements and therefor the checkflights function does not run properly as the db is considered null.
Any solution? code here below. Thank you in advance for your support.
var db = null
const request = indexedDB.open('MyDataBase', '1')
//on upgrade needed
request.onupgradeneeded = e => {
var db = e.target.result
/* note = {
title: "note1",
text: "this is a note"
}*/
const myFlights = db.createObjectStore("my_flight", {
keyPath: "flightid"
})
}
request.onsuccess = e => {
var db = e.target.result
}
request.onerror = e => {
alert(`error: ${e.target.error} was found `)
}
window.onload = function () {
checkFlights()
}
function checkFlights() {
const tx = db.transaction("my_flight", "readonly");
// var objectStore = transaction.objectStore('my_flight');
const mesVols=tx.objectStore("my_flight")
var countRequest = mesVols.count();
countRequest.onsuccess = function() {
console.log(countRequest.result);
if(countRequest.result>0 && window.navigator.onLine){
sendFlights()
notify("Flights sent to server")
}
}
}

You are redeclaring db from the outer scope, by using var again.
When using var in a local scope, you are not affecting the variable from the outer scope and actually creating a new local db variable.
var db = null
const request = indexedDB.open('MyDataBase', '1');
//on upgrade needed
request.onupgradeneeded = e => {
db = e.target.result
/* note = {
title: "note1",
text: "this is a note"
}*/
const myFlights = db.createObjectStore("my_flight", {
keyPath: "flightid"
})
}
request.onsuccess = e => {
db = e.target.result
}
request.onerror = e => {
alert(`error: ${e.target.error} was found `)
}
window.onload = function () {
checkFlights()
}
function checkFlights() {
const tx = db.transaction("my_flight", "readonly");
// var objectStore = transaction.objectStore('my_flight');
const mesVols=tx.objectStore("my_flight")
var countRequest = mesVols.count();
countRequest.onsuccess = function() {
console.log(countRequest.result);
if(countRequest.result>0 && window.navigator.onLine){
sendFlights()
notify("Flights sent to server")
}
}
}
As suggested by #Kinglish in a comment above, you might need to wait for the request to be handled. IndexedDB does not return a promise but you could write an async/await wrapper yourself around the top part or consider using a library like https://github.com/jakearchibald/idb that will Promisify indexedDB.

Wait for all Firebase data query requests before executing code

I am trying to fetch data from different collections in my cloud Firestore database in advance before I process them and apply them to batch, I created two async functions, one to capture the data and another to execute certain code only after all data is collected, I didn't want the code executing and creating errors before the data is fetched when i try to access the matchesObject after the async function to collect data is finished, it keeps saying "it cannot access a property matchStatus of undefined", i thought took care of that with async and await? could anyone shed some light as to why it is undefined one moment
axios.request(options).then(function(response) {
console.log('Total matches count :' + response.data.matches.length);
const data = response.data;
var matchesSnapshot;
var marketsSnapshot;
var tradesSnapshot;
var betsSnapshot;
matchesObject = {};
marketsObject = {};
tradesObject = {};
betsObject = {};
start();
async function checkDatabase() {
matchesSnapshot = await db.collection('matches').get();
matchesSnapshot.forEach(doc => {
matchesObject[doc.id] = doc.data();
console.log('matches object: ' + doc.id.toString())
});
marketsSnapshot = await db.collection('markets').get();
marketsSnapshot.forEach(doc2 => {
marketsObject[doc2.id] = doc2.data();
console.log('markets object: ' + doc2.id.toString())
});
tradesSnapshot = await db.collection('trades').get();
tradesSnapshot.forEach(doc3 => {
tradesObject[doc3.id] = doc3.data();
console.log('trades object: ' + doc3.id.toString())
});
betsSnapshot = await db.collection('bets').get();
betsSnapshot.forEach(doc4 => {
betsObject[doc4.id] = doc4.data();
console.log('bets object: ' + doc4.id.toString())
});
}
async function start() {
await checkDatabase();
// this is the part which is undefined, it keeps saying it cant access property matchStatus of undefined
console.log('here is matches object ' + matchesObject['302283']['matchStatus']);
if (Object.keys(matchesObject).length != 0) {
for (let bets of Object.keys(betsObject)) {
if (matchesObject[betsObject[bets]['tradeMatchId']]['matchStatus'] == 'IN_PLAY' && betsObject[bets]['matched'] == false) {
var sfRef = db.collection('users').doc(betsObject[bets]['user']);
batch11.set(sfRef, {
accountBalance: admin.firestore.FieldValue + parseFloat(betsObject[bets]['stake']),
}, {
merge: true
});
var sfRef = db.collection('bets').doc(bets);
batch12.set(sfRef, {
tradeCancelled: true,
}, {
merge: true
});
}
}
}
});

There are too many smaller issues in the current code to try to debug them one-by-one, so this refactor introduces various tests against your data. It currently won't make any changes to your database and is meant to be a replacement for your start() function.
One of the main differences against your current code is that it doesn't unnecessarily download 4 collections worth of documents (two of them aren't even used in the code you've included).
Steps
First, it will get all the bet documents that have matched == false. From these documents, it will check if they have any syntax errors and report them to the console. For each valid bet document, the ID of it's linked match document will be grabbed so we can then fetch all the match documents we actually need. Then we queue up the changes to the user's balance and the bet's document. Finally we report about any changes to be done and commit them (once you uncomment the line).
Code
Note: fetchDocumentById() is defined in this gist. Its a helper function to allow someCollectionRef.where(FieldPath.documentId(), 'in', arrayOfIds) to take more than 10 IDs at once.
async function applyBalanceChanges() {
const betsCollectionRef = db.collection('bets');
const matchesCollectionRef = db.collection('matches');
const usersCollectionRef = db.collection('users');
const betDataMap = {}; // Record<string, BetData>
await betsCollectionRef
.where('matched', '==', false)
.get()
.then((betsSnapshot) => {
betsSnapshot.forEach(betDoc => {
betDataMap[betDoc.id] = betDoc.data();
});
});
const matchDataMap = {}; // Record<string, MatchData | undefined>
// betIdList contains all IDs that will be processed
const betIdList = Object.keys(betDataMap).filter(betId => {
const betData = betDataMap[betId];
if (!betData) {
console.log(`WARN: Skipped Bet #${betId} because it was falsy (actual value: ${betData})`);
return false;
}
const matchId = betData.tradeMatchId;
if (!matchId) {
console.log(`WARN: Skipped Bet #${betId} because it had a falsy match ID (actual value: ${matchId})`);
return false;
}
if (!betData.user) {
console.log(`WARN: Skipped Bet #${betId} because it had a falsy user ID (actual value: ${userId})`);
return false;
}
const stakeAsNumber = Number(betData.stake); // not using parseFloat as it's too lax
if (isNaN(stakeAsNumber)) {
console.log(`WARN: Skipped Bet #${betId} because it had an invalid stake value (original NaN value: ${betData.stake})`);
return false;
}
matchDataMap[matchId] = undefined; // using undefined because its the result of `doc.data()` when the document doesn't exist
return true;
});
await fetchDocumentsById(
matchesCollectionRef,
Object.keys(matchIdMap),
(matchDoc) => matchDataMap[matchDoc.id] = matchDoc.data()
);
const batch = db.batch();
const queuedUpdates = 0;
betIdList.forEach(betId => {
const betData = betDataMap[betId];
const matchData = matchDataMap[betData.tradeMatchId];
if (matchData === undefined) {
console.log(`WARN: Skipped /bets/${betId}, because it's linked match doesn't exist!`);
continue;
}
if (matchData.matchStatus !== 'IN_PLAY') {
console.log(`INFO: Skipped /bets/${betId}, because it's linked match status is not "IN_PLAY" (actual value: ${matchData.matchStatus})`);
continue;
}
const betRef = betsCollectionRef.doc(betId);
const betUserRef = usersCollectionRef.doc(betData.user);
batch.update(betUserRef, { accountBalance: admin.firestore.FieldValue.increment(Number(betData.stake)) });
batch.update(betRef, { tradeCancelled: true });
queuedUpdates += 2; // for logging
});
console.log(`INFO: Batch currently has ${queuedUpdates} queued`);
// only uncomment when you are ready to make changes
// batch.commit();
}
Usage:
axios.request(options)
.then(function(response) {
const data = response.data;
console.log('INFO: Total matches count from API:' + data.matches.length);
return applyBalanceChanges();
}

Node.Js doesn't execute anonymous functions?? -aws lambda -alexa skill

I'm currently working on a Alexa Skill for my Smart Home.
I created a Lambda function and want to make a http request to a server. but it wont execute any of my anon. functions.
A lambda code example:
/* This code has been generated from your interaction model by skillinator.io
/* eslint-disable func-names */
/* eslint quote-props: ["error", "consistent"]*/
// There are three sections, Text Strings, Skill Code, and Helper Function(s).
// You can copy and paste the contents as the code for a new Lambda function, using the alexa-skill-kit-sdk-factskill template.
// This code includes helper functions for compatibility with versions of the SDK prior to 1.0.9, which includes the dialog directives.
// 1. Text strings =====================================================================================================
// Modify these strings and messages to change the behavior of your Lambda function
const request = require("request");
let speechOutput;
let reprompt;
let welcomeOutput = "Hallo xyz!";
let welcomeReprompt = "xy";
// 2. Skill Code =======================================================================================================
"use strict";
const Alexa = require('alexa-sdk');
const APP_ID = "my id"; // TODO replace with your app ID (OPTIONAL).
speechOutput = '';
const handlers = {
'LaunchRequest': function () {
this.emit(':ask', welcomeOutput, welcomeReprompt);
},
'AMAZON.HelpIntent': function () {
speechOutput = 'Placeholder response for AMAZON.HelpIntent.';
reprompt = '';
this.emit(':ask', speechOutput, reprompt);
},
'AMAZON.CancelIntent': function () {
speechOutput = 'Placeholder response for AMAZON.CancelIntent';
this.emit(':tell', speechOutput);
},
'AMAZON.StopIntent': function () {
speechOutput = 'Placeholder response for AMAZON.StopIntent.';
this.emit(':tell', speechOutput);
},
'SessionEndedRequest': function () {
speechOutput = '';
//this.emit(':saveState', true);//uncomment to save attributes to db on session end
this.emit(':tell', speechOutput);
},
'LichtIntent': function () {
//delegate to Alexa to collect all the required slot values
let filledSlots = delegateSlotCollection.call(this);
speechOutput = '';
//any intent slot variables are listed here for convenience
let zimmerSlotRaw = this.event.request.intent.slots.zimmer.value;
console.log(zimmerSlotRaw);
let zimmerSlot = resolveCanonical(this.event.request.intent.slots.zimmer);
console.log(zimmerSlot);
let was_lichtSlotRaw = this.event.request.intent.slots.was_licht.value;
console.log(was_lichtSlotRaw);
let was_lichtSlot = resolveCanonical(this.event.request.intent.slots.was_licht);
console.log(was_lichtSlot);
//THIS IS THE PART WHERE I NEED HELP!!
MakeRequest(function(data){
console.log("asddd");
speechOutput = "This is a place holder response for the intent named LichtIntent, which includes dialogs. This intent has 2 slots, which are zimmer, and was_licht. Anything else?";
var speechOutput = data;
this.emit(':ask', speechOutput, speechOutput);
});
console.log("asdww");
//DOWN TO HERE!!
},
'StromIntent': function () {
//delegate to Alexa to collect all the required slot values
let filledSlots = delegateSlotCollection.call(this);
speechOutput = '';
//any intent slot variables are listed here for convenience
let geraet_stromSlotRaw = this.event.request.intent.slots.geraet_strom.value;
console.log(geraet_stromSlotRaw);
let geraet_stromSlot = resolveCanonical(this.event.request.intent.slots.geraet_strom);
console.log(geraet_stromSlot);
let wasSlotRaw = this.event.request.intent.slots.was.value;
console.log(wasSlotRaw);
let wasSlot = resolveCanonical(this.event.request.intent.slots.was);
console.log(wasSlot);
//Your custom intent handling goes here
speechOutput = "This is a place holder response for the intent named StromIntent, which includes dialogs. This intent has 2 slots, which are geraet_strom, and was. Anything else?";
this.emit(':ask', speechOutput, speechOutput);
},
'FrageIntent': function () {
//delegate to Alexa to collect all the required slot values
let filledSlots = delegateSlotCollection.call(this);
speechOutput = '';
//any intent slot variables are listed here for convenience
let geraetSlotRaw = this.event.request.intent.slots.geraet.value;
console.log(geraetSlotRaw);
let geraetSlot = resolveCanonical(this.event.request.intent.slots.geraet);
console.log(geraetSlot);
let was_frageSlotRaw = this.event.request.intent.slots.was_frage.value;
console.log(was_frageSlotRaw);
let was_frageSlot = resolveCanonical(this.event.request.intent.slots.was_frage);
console.log(was_frageSlot);
//Your custom intent handling goes here
speechOutput = "This is a place holder response for the intent named FrageIntent, which includes dialogs. This intent has 2 slots, which are geraet, and was_frage. Anything else?";
this.emit(':ask', speechOutput, speechOutput);
},
'TuerIntent': function () {
//delegate to Alexa to collect all the required slot values
let filledSlots = delegateSlotCollection.call(this);
speechOutput = '';
//any intent slot variables are listed here for convenience
let zeitSlotRaw = this.event.request.intent.slots.zeit.value;
console.log(zeitSlotRaw);
let zeitSlot = resolveCanonical(this.event.request.intent.slots.zeit);
console.log(zeitSlot);
//Your custom intent handling goes here
speechOutput = "This is a place holder response for the intent named TuerIntent, which includes dialogs. This intent has one slot, which is zeit. Anything else?";
this.emit(':ask', speechOutput, speechOutput);
},
'Unhandled': function () {
speechOutput = "The skill didn't quite understand what you wanted. Do you want to try something else?";
this.emit(':ask', speechOutput, speechOutput);
}
};
exports.handler = (event, context) => {
const alexa = Alexa.handler(event, context);
alexa.appId = APP_ID;
// To enable string internationalization (i18n) features, set a resources object.
//alexa.resources = languageStrings;
alexa.registerHandlers(handlers);
//alexa.dynamoDBTableName = 'DYNAMODB_TABLE_NAME'; //uncomment this line to save attributes to DB
alexa.execute();
};
// END of Intent Handlers {} ========================================================================================
// 3. Helper Function =================================================================================================
//THESE ARE MY HELPER FUNCTIONS
function url(){
console.log("asd");
return " my server ip";
}
function MakeRequest(callback){
console.log("hallo!");
request.get(url(), function(error, response, body){
console.log("****************************************");
console.log(response);
console.log("****************************************");
console.log(error);
console.log("****************************************");
console.log(body);
console.log("****************************************");
callback("erfolg!");
});
console.log("hffggh");
}
//DOWN TO HERE!!
function resolveCanonical(slot){
//this function looks at the entity resolution part of request and returns the slot value if a synonyms is provided
let canonical;
try{
canonical = slot.resolutions.resolutionsPerAuthority[0].values[0].value.name;
}catch(err){
console.log(err.message);
canonical = slot.value;
};
return canonical;
};
function delegateSlotCollection(){
console.log("in delegateSlotCollection");
console.log("current dialogState: "+this.event.request.dialogState);
if (this.event.request.dialogState === "STARTED") {
console.log("in Beginning");
let updatedIntent= null;
// updatedIntent=this.event.request.intent;
//optionally pre-fill slots: update the intent object with slot values for which
//you have defaults, then return Dialog.Delegate with this updated intent
// in the updatedIntent property
//this.emit(":delegate", updatedIntent); //uncomment this is using ASK SDK 1.0.9 or newer
//this code is necessary if using ASK SDK versions prior to 1.0.9
if(this.isOverridden()) {
return;
}
this.handler.response = buildSpeechletResponse({
sessionAttributes: this.attributes,
directives: getDialogDirectives('Dialog.Delegate', updatedIntent, null),
shouldEndSession: false
});
this.emit(':responseReady', updatedIntent);
} else if (this.event.request.dialogState !== "COMPLETED") {
console.log("in not completed");
// return a Dialog.Delegate directive with no updatedIntent property.
//this.emit(":delegate"); //uncomment this is using ASK SDK 1.0.9 or newer
//this code necessary is using ASK SDK versions prior to 1.0.9
if(this.isOverridden()) {
return;
}
this.handler.response = buildSpeechletResponse({
sessionAttributes: this.attributes,
directives: getDialogDirectives('Dialog.Delegate', null, null),
shouldEndSession: false
});
this.emit(':responseReady');
} else {
console.log("in completed");
console.log("returning: "+ JSON.stringify(this.event.request.intent));
// Dialog is now complete and all required slots should be filled,
// so call your normal intent handler.
return this.event.request.intent;
}
}
function randomPhrase(array) {
// the argument is an array [] of words or phrases
let i = 0;
i = Math.floor(Math.random() * array.length);
return(array[i]);
}
function isSlotValid(request, slotName){
let slot = request.intent.slots[slotName];
//console.log("request = "+JSON.stringify(request)); //uncomment if you want to see the request
let slotValue;
//if we have a slot, get the text and store it into speechOutput
if (slot && slot.value) {
//we have a value in the slot
slotValue = slot.value.toLowerCase();
return slotValue;
} else {
//we didn't get a value in the slot.
return false;
}
}
//These functions are here to allow dialog directives to work with SDK versions prior to 1.0.9
//will be removed once Lambda templates are updated with the latest SDK
function createSpeechObject(optionsParam) {
if (optionsParam && optionsParam.type === 'SSML') {
return {
type: optionsParam.type,
ssml: optionsParam['speech']
};
} else {
return {
type: optionsParam.type || 'PlainText',
text: optionsParam['speech'] || optionsParam
};
}
}
function buildSpeechletResponse(options) {
let alexaResponse = {
shouldEndSession: options.shouldEndSession
};
if (options.output) {
alexaResponse.outputSpeech = createSpeechObject(options.output);
}
if (options.reprompt) {
alexaResponse.reprompt = {
outputSpeech: createSpeechObject(options.reprompt)
};
}
if (options.directives) {
alexaResponse.directives = options.directives;
}
if (options.cardTitle && options.cardContent) {
alexaResponse.card = {
type: 'Simple',
title: options.cardTitle,
content: options.cardContent
};
if(options.cardImage && (options.cardImage.smallImageUrl || options.cardImage.largeImageUrl)) {
alexaResponse.card.type = 'Standard';
alexaResponse.card['image'] = {};
delete alexaResponse.card.content;
alexaResponse.card.text = options.cardContent;
if(options.cardImage.smallImageUrl) {
alexaResponse.card.image['smallImageUrl'] = options.cardImage.smallImageUrl;
}
if(options.cardImage.largeImageUrl) {
alexaResponse.card.image['largeImageUrl'] = options.cardImage.largeImageUrl;
}
}
} else if (options.cardType === 'LinkAccount') {
alexaResponse.card = {
type: 'LinkAccount'
};
} else if (options.cardType === 'AskForPermissionsConsent') {
alexaResponse.card = {
type: 'AskForPermissionsConsent',
permissions: options.permissions
};
}
let returnResult = {
version: '1.0',
response: alexaResponse
};
if (options.sessionAttributes) {
returnResult.sessionAttributes = options.sessionAttributes;
}
return returnResult;
}
function getDialogDirectives(dialogType, updatedIntent, slotName) {
let directive = {
type: dialogType
};
if (dialogType === 'Dialog.ElicitSlot') {
directive.slotToElicit = slotName;
} else if (dialogType === 'Dialog.ConfirmSlot') {
directive.slotToConfirm = slotName;
}
if (updatedIntent) {
directive.updatedIntent = updatedIntent;
}
return [directive];
}
I use the "request" module for my http-request, I think you all know this module.
When I test my function, it gives me NO runtime error!
but the anonymous functions from the MakeRequest call and the request.get call wont execute, and I don't know why.
For Example the console output:
Hallo!,
Asd (very funny.. it gets the params for the request.get.. the bug has to be between the second param(the anon function itself?) in the call and the start of the anon function),
hffggh,
asdww
-the console.logs in the anon. functions doesn't show.
I maybe undestand why the MakeRequest funct. doesn't run -> because the callback from it never came. But why does the request.get not work?? I pasted the necessary parts (the MakeRequest and the helper functions) in a normal node projekt, and it worked!!? -facepalm.... im nearly crying..
My Goal: I want to receive a response from the server.. - thats all. But it just wont go into the function where I can access the response object(s).
(Scroll down to the helper functions)
Please help me out guys, I could really hit my head against the wall.
Reguards

Workaround for new Edge Indexeddb bug?

Microsoft released update kb4088776 in the past couple days, which has had a devastating effect on performance of indexedDb openCursor.
The simple fiddle here shows the problem. With the update, the "retrieval" time is 40 seconds or more. Prior to the update, it is around 1 second.
https://jsfiddle.net/L7q55ad6/23/
Relevant retrieval portion is here:
var _currentVer = 1;
function _openDatabase(fnSuccess) {
var _custDb = window.indexedDB.open("MyDatabase", _currentVer);
_custDb.onsuccess = function (event) {
var db = event.target.result;
fnSuccess(db);
}
_custDb.onerror = function (event) {
_custDb = null;
fnSuccess(null); // should use localData
}
_custDb.onupgradeneeded = function (event) {
var db = event.target.result;
var txn = event.target.transaction;
// Create an objectStore for this database
if (event.oldVersion < _currentVer) {
var customer = db.createObjectStore("customer", { keyPath: "guid" });
var index = customer.createIndex("by_id", "id", { unique: false });
}
};
}
function _retrieveCustomers(fn) {
_openDatabase(function (db) {
if (db == null)
{
alert("not supported");
return;
}
var customers = [];
var transaction = db.transaction("customer", "readonly");
var objectStore = transaction.objectStore("customer");
if (typeof objectStore.getAll === 'function') {
console.log("using getAll");
objectStore.getAll().onsuccess = function (event) {
fn(event.target.result);
};
}
else {
console.log("using openCursor");
objectStore.openCursor().onsuccess = function (event) {
var cursor = event.target.result;
if (cursor) {
customers.push(cursor.value);
cursor.continue();
}
else {
fn(customers);
}
};
}
});
}
The time to create and add the customers is basically normal, only the retrieval is bad. Edge has never supported the getAll method and it still doesn't after the update.
The only workaround I can think of would be to use localStorage instead, but unfortunately our data set is too large to fit into the 10MB limit. It is actually faster now to retrieve from our servers and convert the text to javascript objects, defeating the main purpose of indexeddb.

I don't have Edge so I can't test this, but does it happen with get too, or just openCursor? If get still performs well, you could store an index (in your example, the list of primary keys; in your real app, maybe something more complicated) in localStorage, and then use that to call get on each one.

Limit number of records in firebase

Every minute I have a script that push a new record in my firebase database.
What i want is delete the last records when length of the list reach a fixed value.
I have been through the doc and other post and the thing I have found so far is something like that :
// Max number of lines of the chat history.
const MAX_ARDUINO = 10;
exports.arduinoResponseLength = functions.database.ref('/arduinoResponse/{res}').onWrite(event => {
const parentRef = event.data.ref.parent;
return parentRef.once('value').then(snapshot => {
if (snapshot.numChildren() >= MAX_ARDUINO) {
let childCount = 0;
let updates = {};
snapshot.forEach(function(child) {
if (++childCount <= snapshot.numChildren() - MAX_ARDUINO) {
updates[child.key] = null;
}
});
// Update the parent. This effectively removes the extra children.
return parentRef.update(updates);
}
});
});
The problem is : onWrite seems to download all the related data every time it is triggered.
This is a pretty good process when the list is not so long. But I have like 4000 records, and every month it seems that I screw up my firebase download quota with that.
Does anyone would know how to handle this kind of situation ?

Ok so at the end I came with 3 functions. One update the number of arduino records, one totally recount it if the counter is missing. The last one use the counter to make a query using the limitToFirst filter so it retrieve only the relevant data to remove.
It is actually a combination of those two example provided by Firebase :
https://github.com/firebase/functions-samples/tree/master/limit-children
https://github.com/firebase/functions-samples/tree/master/child-count
Here is my final result
const MAX_ARDUINO = 1500;
exports.deleteOldArduino = functions.database.ref('/arduinoResponse/{resId}/timestamp').onWrite(event => {
const collectionRef = event.data.ref.parent.parent;
const countRef = collectionRef.parent.child('arduinoResCount');
return countRef.once('value').then(snapCount => {
return collectionRef.limitToFirst(snapCount.val() - MAX_ARDUINO).transaction(snapshot => {
snapshot = null;
return snapshot;
})
});
});
exports.trackArduinoLength = functions.database.ref('/arduinoResponse/{resId}/timestamp').onWrite(event => {
const collectionRef = event.data.ref.parent.parent;
const countRef = collectionRef.parent.child('arduinoResCount');
// Return the promise from countRef.transaction() so our function
// waits for this async event to complete before it exits.
return countRef.transaction(current => {
if (event.data.exists() && !event.data.previous.exists()) {
return (current || 0) + 1;
} else if (!event.data.exists() && event.data.previous.exists()) {
return (current || 0) - 1;
}
}).then(() => {
console.log('Counter updated.');
});
});
exports.recountArduino = functions.database.ref('/arduinoResCount').onWrite(event => {
if (!event.data.exists()) {
const counterRef = event.data.ref;
const collectionRef = counterRef.parent.child('arduinoResponse');
// Return the promise from counterRef.set() so our function
// waits for this async event to complete before it exits.
return collectionRef.once('value')
.then(arduinoRes => counterRef.set(arduinoRes.numChildren()));
}
});
I have not tested it yet but soon I will post my result !
I also heard that one day Firebase will add a "size" query, that is definitely missing in my opinion.