I am using Firebase Cloud Firestore, however, I think this may be more of a JavaScript promise issue.
I have a collection called "students" which I am querying. For each found student I want to issue another query to find "parents" related by id.
For this, I have to nest a promise / foreach query and result inside another promise / foreach query and result.
Its currently executing the entire "students" promise/loop, returning from the function, then executing each of the "parents" promise/loops afterwards.
I want it to step through one found student, then execute all parents for that student, then go onto the next student, then return from the function.
getStudents(grade) {
let grade_part = this.getGrade(grade);
var dbRef = db.collection("students");
var dbQuery = dbRef.where('bb_current_grade', '==', grade_part);
var dbPromise = dbQuery.get();
var allStudents = [];
return dbPromise.then(function(querySnapshot) {
querySnapshot.forEach(doc => {
console.log("student");
var studentPlusParents = doc.data();
studentPlusParents.parents = [];
var dbRef = db.collection("parents");
var dbQuery = dbRef.where('student_id', '==', doc.data().id);
var dbPromise = dbQuery.get();
dbPromise.then(function(querySnapshot) {
querySnapshot.forEach(parentDoc => {
console.log("Add parent");
studentPlusParents.parents.push(parentDoc.data());
});
});
//console.log(studentPlusParents);
allStudents.push(studentPlusParents)
});
//console.log(allStudents);
return Promise.all(allStudents);
})
.catch(function(error) {
console.log("Error getting documents: ", error);
});
}
Related
I am trying to make barbershop web app where costumer can see list of free appointments and when they reserve free appointment I want to delete that field from firebase.
I have a collection which represents one barber.
This is how it looks in firebase.
As you see radno_vrijeme is object or map in firebase which contains 6 arrays, and in each array there is list of free working hours.
In my function I am able to do everthing except last line where I need to update firebase collection.
const finishReservation = async () => {
try {
const freeTimeRef = collection(db, `${barber}`);
const q = query(freeTimeRef);
const querySnap = await getDoc(q);
querySnap.forEach(async (doc) => {
const radnoVrijeme = doc.data().radno_vrijeme;
// Find the index of the hour you want to delete
const index = radnoVrijeme["Mon"].indexOf(hour);
// Remove the hour from the array
radnoVrijeme["Mon"].splice(index, 1);
// Update the document in the collection
console.log(radnoVrijeme);
const radnoVrijemeMap = new Map(Object.entries(radnoVrijeme));
await freeTimeRef.update({ radno_vrijeme: radnoVrijemeMap });
});
} catch (error) {
console.log(error);
}
};
I tried to pass it as JSON stringified object, but it didn't work. I always get this error :
"FirebaseError: Expected type 'ya', but it was: a custom Ia object"
When you are trying to fetch multiple documents using a collection reference or query, then you must use getDocs():
const finishReservation = async () => {
try {
const freeTimeRef = collection(db, `${barber}`);
const q = query(freeTimeRef);
const querySnap = await getDocs(q);
const updates = [];
querySnap.forEach((d) => {
const radnoVrijeme = d.data().radno_vrijeme;
const index = radnoVrijeme["Mon"].indexOf(hour);
radnoVrijeme["Mon"].splice(index, 1);
const radnoVrijemeMap = new Map(Object.entries(radnoVrijeme));
updates.push(updateDoc(d.ref, { radno_vrijeme: radnoVrijemeMap }))
});
await Promise.all(updates);
console.log("Documents updated")
} catch (error) {
console.log(error);
}
};
getDoc() is used to fetch a single document using a document reference.
Problem Statement:
Our aim is to allocate values in the array ytQueryAppJs, which are returned from a time consuming function httpsYtGetFunc().
The values in ytQueryAppJs needs to be used many times in further part of the code, hence it needs to be done 'filled', before the code proceeds further.
There are many other arrays like ytQueryAppJs, namely one of them is ytCoverAppJs, that needs to be allocated the value, the same way as ytQueryAppJs.
The values in ytCoverAppJs further require the use of values from ytQueryAppJs. So a solution with clean code would be highly appreciated.
(I am an absolute beginner. I have never used async, await or promises and I'm unaware of the correct way to use it. Please guide.)
Flow (to focus on):
The user submits a queryValue in index.html.
An array ytQueryAppJs is logged in console, based on the query.
Expected Log in Console (similar to):
Current Log in Console:
Flow (originally required by the project):
User submits query in index.html.
The values of arrays, ytQueryAppJs, ytCoverAppJs, ytCoverUniqueAppJs, ytLiveAppJs, ytLiveUniqueAppJs gets logged in the console, based on the query.
Code to focus on, from 'app.js':
// https://stackoverflow.com/a/14930567/14597561
function compareAndRemove(removeFromThis, compareToThis) {
return (removeFromThis = removeFromThis.filter(val => !compareToThis.includes(val)));
}
// Declaring variables for the function 'httpsYtGetFunc'
let apiKey = "";
let urlOfYtGetFunc = "";
let resultOfYtGetFunc = "";
let extractedResultOfYtGetFunc = [];
// This function GETs data, parses it, pushes required values in an array.
async function httpsYtGetFunc(queryOfYtGetFunc) {
apiKey = "AI...MI"
urlOfYtGetFunc = "https://www.googleapis.com/youtube/v3/search?key=" + apiKey + "&part=snippet&q=" + queryOfYtGetFunc + "&maxResults=4&order=relevance&type=video";
let promise = new Promise((resolve, reject) => {
// GETting data and storing it in chunks.
https.get(urlOfYtGetFunc, (response) => {
const chunks = []
response.on('data', (d) => {
chunks.push(d)
})
// Parsing the chunks
response.on('end', () => {
resultOfYtGetFunc = JSON.parse((Buffer.concat(chunks).toString()))
// console.log(resultOfYtGetFunc)
// Extracting useful data, and allocating it.
for (i = 0; i < (resultOfYtGetFunc.items).length; i++) {
extractedResultOfYtGetFunc[i] = resultOfYtGetFunc.items[i].id.videoId;
// console.log(extractedResultOfYtGetFunc);
}
resolve(extractedResultOfYtGetFunc);
})
})
})
let result = await promise;
return result;
}
app.post("/", function(req, res) {
// Accessing the queryValue, user submitted in index.html. We're using body-parser package here.
query = req.body.queryValue;
// Fetching top results related to user's query and putting them in the array.
ytQueryAppJs = httpsYtGetFunc(query);
console.log("ytQueryAppJs:");
console.log(ytQueryAppJs);
});
Complete app.post method from app.js:
(For better understanding of the problem.)
app.post("/", function(req, res) {
// Accessing the queryValue user submitted in index.html.
query = req.body.queryValue;
// Fetcing top results related to user's query and putting them in the array.
ytQueryAppJs = httpsYtGetFunc(query);
console.log("ytQueryAppJs:");
console.log(ytQueryAppJs);
// Fetching 'cover' songs related to user's query and putting them in the array.
if (query.includes("cover") == true) {
ytCoverAppJs = httpsYtGetFunc(query);
console.log("ytCoverAppJs:");
console.log(ytCoverAppJs);
// Removing redundant values.
ytCoverUniqueAppJs = compareAndRemove(ytCoverAppJs, ytQueryAppJs);
console.log("ytCoverUniqueAppJs:");
console.log(ytCoverUniqueAppJs);
} else {
ytCoverAppJs = httpsYtGetFunc(query + " cover");
console.log("ytCoverAppJs:");
console.log(ytCoverAppJs);
// Removing redundant values.
ytCoverUniqueAppJs = compareAndRemove(ytCoverAppJs, ytQueryAppJs);
console.log("ytCoverUniqueAppJs:");
console.log(ytCoverUniqueAppJs);
}
// Fetching 'live performances' related to user's query and putting them in the array.
if (query.includes("live") == true) {
ytLiveAppJs = httpsYtGetFunc(query);
console.log("ytLiveAppJs:");
console.log(ytLiveAppJs);
// Removing redundant values.
ytLiveUniqueAppJs = compareAndRemove(ytLiveAppJs, ytQueryAppJs.concat(ytCoverUniqueAppJs));
console.log("ytLiveUniqueAppJs:");
console.log(ytLiveUniqueAppJs);
} else {
ytLiveAppJs = httpsYtGetFunc(query + " live");
console.log("ytLiveAppJs:");
console.log(ytLiveAppJs);
// Removing redundant values.
ytLiveUniqueAppJs = compareAndRemove(ytLiveAppJs, ytQueryAppJs.concat(ytCoverUniqueAppJs));
console.log("ytLiveUniqueAppJs:");
console.log(ytLiveUniqueAppJs);
}
// Emptying all the arrays.
ytQueryAppJs.length = 0;
ytCoverAppJs.length = 0;
ytCoverUniqueAppJs.length = 0;
ytLiveAppJs.length = 0;
ytLiveUniqueAppJs.length = 0;
});
Unfortunately you can use the async/await on http module when making requests. You can install and use axios module . In your case it will be something like this
const axios = require('axios');
// Declaring variables for the function 'httpsYtGetFunc'
let apiKey = "";
let urlOfYtGetFunc = "";
let resultOfYtGetFunc = "";
let extractedResultOfYtGetFunc = [];
// This function GETs data, parses it, pushes required values in an array.
async function httpsYtGetFunc(queryOfYtGetFunc) {
apiKey = "AI...MI"
urlOfYtGetFunc = "https://www.googleapis.com/youtube/v3/search?key=" + apiKey + "&part=snippet&q=" + queryOfYtGetFunc + "&maxResults=4&order=relevance&type=video";
const promise = axios.get(urlOfYtGetFunc).then(data => {
//do your data manipulations here
})
.catch(err => {
//decide what happens on error
})
Or async await
const data = await axios.get(urlOfYtGetFunc);
//Your data variable will become what the api has returned
If you still want to catch errors on async await you can use try catch
try{
const data = await axios.get(urlOfYtGetFunc);
}catch(err){
//In case of error do something
}
I have just looked at the code I think the issue is how you are handling the async code in the request handler. You are not awaiting the result of the function call to httpsYtGetFunc in the body so when it returns before the promise is finished which is why you get the Promise {Pending}.
Another issue is that the array is not extractedResultOfYtGetFunc is not initialised and you may access indexes that don't exist. The method to add an item to the array is push.
To fix this you need to restructure your code slightly. A possible solution is something like this,
// Declaring variables for the function 'httpsYtGetFunc'
let apiKey = "";
let urlOfYtGetFunc = "";
let resultOfYtGetFunc = "";
let extractedResultOfYtGetFunc = [];
// This function GETs data, parses it, pushes required values in an array.
function httpsYtGetFunc(queryOfYtGetFunc) {
apiKey = "AI...MI";
urlOfYtGetFunc =
"https://www.googleapis.com/youtube/v3/search?key=" +
apiKey +
"&part=snippet&q=" +
queryOfYtGetFunc +
"&maxResults=4&order=relevance&type=video";
return new Promise((resolve, reject) => {
// GETting data and storing it in chunks.
https.get(urlOfYtGetFunc, (response) => {
const chunks = [];
response.on("data", (d) => {
chunks.push(d);
});
// Parsing the chunks
response.on("end", () => {
// Initialising the array
extractedResultOfYtGetFunc = []
resultOfYtGetFunc = JSON.parse(Buffer.concat(chunks).toString());
// console.log(resultOfYtGetFunc)
// Extracting useful data, and allocating it.
for (i = 0; i < resultOfYtGetFunc.items.length; i++) {
// Adding the element to the array
extractedResultOfYtGetFunc.push(resultOfYtGetFunc.items[i].id.videoId);
// console.log(extractedResultOfYtGetFunc);
}
resolve(extractedResultOfYtGetFunc);
});
});
});
}
app.post("/", async function (req, res) {
query = req.body.queryValue;
// Fetching top results related to user's query and putting them in the array.
ytQueryAppJs = await httpsYtGetFunc(query);
console.log("ytQueryAppJs:");
console.log(ytQueryAppJs);
});
Another option would be to use axios,
The code for this would just be,
app.post("/", async function (req, res) {
query = req.body.queryValue;
// Fetching top results related to user's query and putting them in the array.
try{
ytQueryAppJs = await axios.get(url); // replace with your URL
console.log("ytQueryAppJs:");
console.log(ytQueryAppJs);
} catch(e) {
console.log(e);
}
});
Using Axios would be a quicker way as you don't need to write promise wrappers around everything, which is required as the node HTTP(S) libraries don't support promises out of the box.
I'm working with mongodb stitch/realm and I'm trying to modify objects inside an array with a foreach and also pushing ids into a new array.
For each object that i'm modifying, I'm also doing a query first, after the document is found I start modifying the object and then pushing the id into another array so I can use both arrays later.
The code is something like this:
exports = function(orgLoc_id, data){
var HttpStatus = require('http-status-codes');
// Access DB
const db_name = context.values.get("database").name;
const db = context.services.get("mongodb-atlas").db(db_name);
const orgLocPickupPointCollection = db.collection("organizations.pickup_points");
const orgLocStreamsCollection = db.collection("organizations.streams");
const streamsCollection = db.collection("streams");
let stream_ids = [];
data.forEach(function(stream) {
return streamsCollection.findOne({_id: stream.stream_id}, {type: 1, sizes: 1}).then(res => { //if I comment this query it will push without any problem
if(res) {
let newId = new BSON.ObjectId();
stream._id = newId;
stream.location_id = orgLoc_id;
stream.stream_type = res.type;
stream.unit_price = res.sizes[0].unit_price_dropoff;
stream._created = new Date();
stream._modified = new Date();
stream._active = true;
stream_ids.push(newId);
}
})
})
console.log('stream ids: ' + stream_ids);
//TODO
};
But when I try to log 'stream_ids' it's empty and nothing is shown. Properties stream_type and unit_price are not assigned.
I've tried promises but I haven't had success
It's an asynchronous issue. You're populating the value of the array inside a callback. But because of the nature of the event loop, it's impossible that any of the callbacks will have been called by the time the console.log is executed.
You mentioned a solution involving promises, and that's probably the right tack. For example something like the following:
exports = function(orgLoc_id, data) {
// ...
let stream_ids = [];
const promises = data.map(function(stream) {
return streamsCollection.findOne({ _id: stream.stream_id }, { type: 1, sizes: 1 })
.then(res => { //if I comment this query it will push without any problem
if (res) {
let newId = new BSON.ObjectId();
// ...
stream_ids.push(newId);
}
})
})
Promise.all(promises).then(function() {
console.log('stream ids: ' + stream_ids);
//TODO
// any code that needs access to stream_ids should be in here...
});
};
Note the change of forEach to map...that way you're getting an array of all the Promises (I'm assuming your findOne is returning a promise because of the .then).
Then you use a Promise.all to wait for all the promises to resolve, and then you should have your array.
Side note: A more elegant solution would involve returning newId inside your .then. In that case Promise.all will actually resolve with an array of the results of all the promises, which would be the values of newId.
I need to create a new array from iterating mongodb result. This is my code.
const result = await this.collection.find({
referenceIds: {
$in: [referenceId]
}
});
var profiles = [];
result.forEach(row => {
var profile = new HorseProfileModel(row);
profiles.push(profile);
console.log(profiles); //1st log
});
console.log(profiles); //2nd log
I can see update of profiles array in 1st log. But 2nd log print only empty array.
Why i couldn't push item to array?
Update
I think this is not related to promises. HorseProfileModel class is simply format the code.
const uuid = require("uuid");
class HorseProfileModel {
constructor(json, referenceId) {
this.id = json.id || uuid.v4();
this.referenceIds = json.referenceIds || [referenceId];
this.name = json.name;
this.nickName = json.nickName;
this.gender = json.gender;
this.yearOfBirth = json.yearOfBirth;
this.relations = json.relations;
this.location = json.location;
this.profilePicture = json.profilePicture;
this.horseCategory = json.horseCategory;
this.followers = json.followers || [];
}
}
module.exports = HorseProfileModel;
await this.collection.find(...)
that returns an array of the found data right? Nope, that would be to easy. find immeadiately returns a Cursor. Calling forEach onto that does not call the sync Array.forEach but rather Cursor.forEach which is async and weve got a race problem. The solution would be promisifying the cursor to its result:
const result = await this.collection.find(...).toArray();
Reference
SCENARIO:
Using mssql I'm connecting to sql and retrieving a list of ids, then based on those id I want to run stored procedures. What I'm currently doing is running the first stored proc, storing the id's in an array, then I'm running a for loop calling another module, where I pass the id to run a stored proc. This works fine when I've got a single id, but fails with 'Global connection already exists. Call sql.close() first.' when I try to run multiple ones.
How do I create connect to sql, run my query, then run the next one? What's the best approach?
The code below runs the stored proc with ids and causes the above error.
exports.runStoredProc = function (query,id) {
sql.connect(config.config).then(()=>{
return sql.query`${query} ${id}`
}).then(res=> {
do something with the response
}).catch(error => {
console.log(error)
})
}
Looks like the connection still exists when the below bit of code runs it using next id. I thought that creating a Promise will force to await execution before it runs the above bit of code again?
let toRun = result.recordset.length
let gen = async num => {
for(let i=0;i<num;i++) {
var resp = result.recordset[i].id
console.log(i, resp)
var sp = report
var reportId = await new Promise(() => db.runStoredProc(sp,resp))
}
}
gen(toRun).then(() => console.log("done!"))
You need to return Promise from runStoredProc
exports.runStoredProc = function (query,id) {
return sql.connect(config.config).then(()=>{
return sql.query`${query} ${id}`
}).then(res=> {
do something with the response
}).catch(error => {
console.log(error)
})
}
and no need to wrap db.runStoredProc in loop
let toRun = result.recordset.length
let gen = async num => {
for(let i=0;i<num;i++) {
var resp = result.recordset[i].id
console.log(i, resp)
var sp = report
var reportId = await db.runStoredProc(sp,resp)
}
}
gen(toRun).then(() => console.log("done!"))