SyntaxError when calling async await in Loop - javascript

I have a route in my NodeJs app which takes a post request and then retrieves some data with await. The first await in my function works fine but then it complains when i call another function with await. I marked the function which causes the issue with >>>>
SyntaxError: await is only valid in async function
Has this error to do with the forEach Loop and if so how can i fix that
farmRoutes.post('/bulkemail/:farmid', async(req, res) => {
try{
const farmid = req.params.farmid
// Check if we have an Emails Array
if (typeof req.body.emails != 'undefined' && req.body.emails instanceof Array ){
// Assign Emails Array from Body to emails
const emails = req.body.emails
// get the current Emails Array from Farm Doc
let oldEmail = await couch.getSubDoc('contacts', farmid ,'emails')
// Loop thru all emails in the new Array
emails.forEach((email) => {
console.log(email)
// Check if the email is curently already in the Farm Doc
var data = _.find(oldEmail, function(emailItem){ return emailItem.address == email; });
var index =_.indexOf(oldEmail,data);
if (index > -1) {
// Email already Exists will not be created
console.log("Email already in the List")
} else {
// if not in current Farm create new Email object and add to the oldEmail Array
>>>>>var newEmail = await contact.simp_email(simp_email)
// Upsert the updated Email Arra to farm Doc
var success = await cb.insertArrayItem(req.bucket, farmid, "emails", newEmail )
console.log(success)
}
})
} else {
console.log("we have no new emails")
}

Every function that awaits, must be an async function. Including the one passed to forEach.
emails.forEach(async (email) => {
Alternatively, you could avoid creating an iteration function by using a simple for of loop. This is usually preferred to using the forEach since it's a bit simpler and doesn't create any new functions.
for (const email of emails) {
//...
var newEmail = await contact.simp_email(simp_email)
//...
}

Related

How to chain filter and map methods in nodejs?

So I'm working on a project where I'm making a call to a database to retrieve the data stored there. This data comes as an array. here is the code:
const allLogins = await Login.find().sort("name");
const token = req.header("x-auth-token");
const user = jwt.verify(token, config.get("jwtPrivateKey"));
const logins = allLogins
.filter((login) => login.userId === user._id)
.map((login) => {
login.password = decrypt(login.password);
});
If I call a console.log after the decrypt has been run I see that it has been completed correctly. The issue I have is if I console.log(logins) it says it is an array of two items that are both undefined. If instead I run it like this...
const allLogins = await Login.find().sort("name");
const token = req.header("x-auth-token");
const user = jwt.verify(token, config.get("jwtPrivateKey"));
let logins = allLogins.filter((login) => login.userId === user._id);
logins.map((login) => {
login.password = decrypt(login.password);
});
Then it works as it should. I'm not sure why the first set of code doesn't work and why the second set does work.
Any help would be appreciated!
Basic :
array. filter - accept a callback and call back return boolean (that match our criteria)
array.map - accept a callback and call back return transformed object
In the second working example:
logins.map((login) => {
// note: logins is iterated but not assigned to logins back
// so accessing login is working
login.password = decrypt(login.password); // map should return data
+ return login; // if we update all code will work
});
Now coming to first example:
const logins = allLogins
.filter((login) => login.userId === user._id)
.map((login) => {
login.password = decrypt(login.password);
+ return login; // this will fix the issue
});

How to correctly use 'async, await and promises' in nodejs, while allocating values to a variable returned from a time-consuming function?

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.

only one object being set to app.set() Expressjs

Good Afternoon,
I am using the MERN stack to making a simple invoice application.
I have a function that runs 2 forEach() that goes through the invoices in the DB and the Users. if the emails match then it gives the invoices for that user.
When I log DBElement to the console it works, it has the proper data, but when I log test1 to the console (app.get()) it only has one object not both.
// forEach() function
function matchUserAndInvoice(dbInvoices, dbUsers) {
dbInvoices.forEach((DBElement) => {
dbUsers.forEach((userElement) => {
if(DBElement.customer_email === userElement.email){
const arrayNew = [DBElement];
arrayNew.push(DBElement);
app.set('test', arrayNew);
}
})
})
}
// end point that triggers the function and uses the data.
app.get('/test', async (req,res) => {
const invoices = app.get('Invoices');
const users = await fetchUsersFromDB().catch((e) => {console.log(e)});
matchUserAndInvoice(invoices,users,res);
const test1 = await app.get('test');
console.log(test1);
res.json(test1);
})
function matchUserAndInvoice(dbInvoices, dbUsers) {
let newArray = [];
dbInvoices.forEach((DBElement) => {
dbUsers.forEach(async(userElement) => {
if(DBElement.customer_email === userElement.email){
newArray.push(DBElement);
app.set('test', newArray);
}
})
})
}
app.set('test', DBElement); overrides the existing DBElement, so only the last matching DBElement is shown in test1.
If you want to have test correspond to all matching DBElement, you should set it to an array, and then append a new DBElement to the array each time it matches inside the for-loop:
if(DBElement.customer_email === userElement.email){
let newArray = await app.get('test');
newArray.push(DBElement);
app.set('test', newArray);
}

How to use Array contains in two different array fields in firebase for flutter

I have a document with two fields, searchkeys1 and searchkeys2, I want my firebase query to check if a value I provided is present in searchkey1 and return, if not search searchkey2, my first attempt was to create a query with the value and first check searchkey1 and if the documents returned are empty, try searchkey2, my problem is I keep getting an error when I am trying to check if any documents were returned
"the getter 'documents' isn't defined for the type 'Stream<QuerySnapshot>' "
here is my code
startSearch(input) {
var docSnapshot = FirebaseFirestore.instance
.collection('items')
.where('searchkeys1', arrayContains: input.toString()).snapshots();
if (docSnapshot.documents.length == 0) {
var docSnapshot2 = FirebaseFirestore.instance
.collection('items')
.where('searchkeys2', arrayContains: input.toString()).snapshots();
return docSnapshot2;
} else if (docSnapshot.documents.length != 0) {
return docSnapshot;
}
You need to make your function async and use get insted of smnapshots:
startSearch(input) async {
var docSnapshot = await FirebaseFirestore.instance
.collection('items')
.where('searchkeys1', arrayContains: input.toString()).get();
if (docSnapshot.documents.length == 0) {
var docSnapshot2 = await FirebaseFirestore.instance
.collection('items')
.where('searchkeys2', arrayContains: input.toString()).get();
return docSnapshot2;
} else if (docSnapshot.documents.length != 0) {
return docSnapshot;
}
With get you get the data once as you want it. But with snapshots you get a listener for realtime chanegs.

How to query SQL in a loop in node js

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!"))

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