I am trying to push data into the realtime database using a for loop as there are multiple entries. The am confused on how should multiple promises be handled. Please help.
onSubmit() {
for(let i = 0; i < this.userList.length; i++) {
this.mtcService.getUserCount(this.userList[i].$key).subscribe(
((ct) => {
const Mtcount = ct.length;
// pushing to realtime db =>
this.mtcService.createUser(this.userList[i].$key, Mtcount, this.userForm.value)
.then(() => {
console.log('Success ' + i);
}, err => {
console.log(err);
})
}),
((err) => {
console.log(err);
})
);
}
}
getUserCount(id) {
return this.db.list('path1/path2/' + id).snapshotChanges();
}
createUser(path, count, data) {
return this.db.object('path3/path4/' + path + '/' + count).set(data);
}
const promises = data.map(async (id) => {
await Axios.post(URL);
});
await Promise.all(promises);
Related
I am trying to run a query to get some data from a table, then use that array of data to get some data from another table to then return it as JSON.
I have been trying for a while but I cannot seem to figure out async and await. Right now it does sort of work but doesn't wait for my second query in the for loop to finish before returning data.
app.get("/get-top-trending", (request, response) => {
const req = request.query
let query = 'SELECT Ticker, Mentions FROM trend_data ORDER BY Date DESC, ' + req.by + ' DESC LIMIT 3';
let returnData = {};
cryptoDB.query(query, (err, tickers) => {
if (err) throw err;
getData(tickers).then(function() {
response.send(returnData)
});
});
async function getData(tickers) {
for (let i = 0; i < tickers.length; i++) {
cryptoDB.query('SELECT HistoricalJSON FROM historical_trend_data WHERE Ticker=? LIMIT 1', [tickers[i]['Ticker']], (err, rows2) => {
if (err) throw err;
returnData[tickers[i]['Ticker']] = rows2[0]['HistoricalJSON'];
});
}
}
});
I assume that something has to be done in the getData async function, however I am not particularly sure how to implement a working solution. I have tried promises but they don't seem to work the way that I expect.
Any guidance would be appreciated.
first solution:
app.get("/get-top-trending", (request, response) => {
const req = request.query
let query = 'SELECT Ticker, Mentions FROM trend_data ORDER BY Date DESC, ' + req.by + ' DESC LIMIT 3';
cryptoDB.query(query, (err, tickers) => {
if (err) throw err;
getData(tickers).then(function (returnData) {
response.send(returnData)
});
});
async function getData(tickers) {
const returnData = {};
const querys = ((ticker) => {
return new Promise((resolve, reject) => {
cryptoDB.query('SELECT HistoricalJSON FROM historical_trend_data WHERE Ticker=? LIMIT 1', [ticker['Ticker']], (err, rows2) => {
if (err) reject(err);
returnData[ticker['Ticker']] = rows2[0]['HistoricalJSON'];
resolve();
});
})
})
for (let i = 0; i < tickers.length; i++) {
await querys(tickers[i]);
}
return returnData
}
});
second solution:
app.get("/get-top-trending", (request, response) => {
const req = request.query
let query = 'SELECT Ticker, Mentions FROM trend_data ORDER BY Date DESC, ' + req.by + ' DESC LIMIT 3';
cryptoDB.query(query, (err, tickers) => {
if (err) throw err;
getData(tickers).then(function(returnData) {
response.send(returnData)
}).catch(error => throw error);
});
async function getData(tickers) {
let returnData = {};
for (let i = 0; i < tickers.length; i++) {
returnData[tickers[i]['Ticker']] = await getTickerQuery([tickers[i]['Ticker']]);
}
return returnData;
}
function getTickerQuery(ticker) {
return new Promise((resolve, reject) => {
cryptoDB.query('SELECT HistoricalJSON FROM historical_trend_data WHERE Ticker=? LIMIT 1', ticker, (err, rows2) => {
if (err) throw reject(err);
resolve(rows2[0]['HistoricalJSON']);
});
})
}
});
I recommend second solution for readability
I am coding a post request which downloads all URL HTML,zips them and email it back. This all should happen in the backend. I am storing all the data in an array and extract the first element to start these operations.
I have while loop inside which I am calling some functions. Each function gets executed at a certain time.
I used async, await and promises to make sure they run one after the
other.
Coming to my problem.
My while loop starts getting executed again before all the
functions inside it are executed.
app.post('/?', async (req, res) => {
var urls = req.query.urls
var email = req.query.email;
var new_stack = [urls, email]
stack.push(new_stack)
res.send("Mail sent")
if (isFunctionRunning === false) { //initially it is false
console.log(isFunctionRunning, stack.length)
send_mails();
}
});
const getGoogleIndexHTML = (url) => {
return new Promise((resolve, reject) => {
request(url, (err, res, body) => err ? reject(err) : resolve(body))
})
}
const some_function_to_download = async (url) => {
try {
const a = url.split(".")
let googleIndexHTML = await getGoogleIndexHTML(url)
await fs.writeFile(directory + '/' + a[1] + '.html', googleIndexHTML, (err) => {
if (err) throw err
})
console.log('File created.')
} catch (err) {
console.log(err)
}
}
const html_to_zip_file = async () => {
await zipper.zip(directory, function (error, zipped) {
if (!error) {
zipped.compress();
zipped.save('./package.zip', function (error) {
if (!error) {
console.log("Saved successfully !");
}
});
} else {
console.log(error)
}
})
}
const send_mails = async () => {
while (stack.length > 0) {
isFunctionRunning = true
var a = stack.shift()
var urls = a[0]
var collection_urls = urls.split(",");
var to_email = a[1]
rimraf(directory, function () {
console.log("done");
});
fs.mkdirSync(directory);
for (url of collection_urls) {
await some_function_to_download(url); // 5 sec per download
}
await html_to_zip_file() // takes 5 sec to zip
.then(result => {
transporter.sendMail(set_mail_options(to_email)) //2 sec to send mail
.then(result => {
console.log("Mail sent")
})
.catch(err => {
console.log(err)
})
})
.catch(err => {
console.log(err)
})
console.log("reached") // this is reached before zip is done and mail sent. I want to prevent this
}
isFunctionRunning = false
}
You need to return transporter.sendMail in sendMail, fs.writeFile in someFunctionToDownload and zipper.zip in htmlToZipFile otherwise the await won't work as expected (I'm assuming that they actually do return promises, I'm only familiar with fs.writeFile)
Also: CamelCase is used in JS, not snake_case 🙃
And are you sure rimraf is synchronous?
const sendMails = async () => {
while (stack.length > 0) {
isFunctionRunning = true;
const [urls, toEmail] = stack.shift();
var collectionUrls = urls.split(",");
rimraf(directory, function() {
console.log("done");
});
await fs.mkdir(directory);
await Promise.All(collectionUrls.map(someFunctionToDownload)); // 5 sec per download
await htmlToZipFile() // takes 5 sec to zip
.then(result => transporter.sendMail(set_mail_options(toEmail))) //2 sec to send mail
.then(result => {
console.log("Mail sent");
})
.catch(err => {
console.log(err);
});
console.log("reached"); // this is reached before zip is done and mail sent. I want to prevent this
}
isFunctionRunning = false;
};
const someFunctionToDownload = async url => {
const a = url.split(".");
const googleIndexHTML = await getGoogleIndexHTML(url);
return fs.writeFile(`${directory}/${a[1]}.html`, googleIndexHTML, err => {
if (err) throw err;
});
};
const htmlToZipFile = async () => {
return zipper.zip(directory, function(error, zipped) {
if (!error) {
zipped.compress();
zipped.save("./package.zip", function(error) {
if (!error) {
console.log("Saved successfully!");
}
});
} else {
console.log(error);
}
});
};
Try using the following
while (stack.length > 0) {
isFunctionRunning = true
var a = stack.shift()
var urls = a[0]
var collection_urls = urls.split(",");
var to_email = a[1]
rimraf(directory, function () {
console.log("done");
});
fs.mkdirSync(directory);
for (url of collection_urls) {
await some_function_to_download(url); // 5 sec per download
}
try {
const result = await html_to_zip_file() // takes 5 sec to zip
const sendMailResult = await transporter.sendMail(set_mail_options(to_email))
} catch(e)
{
console.log(e)
}
console.log("reached")
}
Since html_to_zip_file() and sendMail function are independent
we can use
const result = await Promise.all([html_to_zip_file(),transporter.sendMail(set_mail_options(to_email))]);
I have two js files. i am able to get data from mongodb by calliing bookDao.getActiveBookByCategoryId().
My Problem
In categoryDao.js file i am trying to update resultJson.book_countinside BookDao.getActiveBookByCategoryId() method. but it is not updating. So may i know how to fix this.
here book_count property in resultJson is still 0.
categoryDao.js
module.exports.getAllActiveCategory = (callback) => {
Category.find({
is_delete : false
}, (error, result) => {
if(error) {
console.log(error);
callback(commonUtil.ERROR);
}
if(result) {
var categoryArray = [];
for(var i=0; i<result.length; i++) {
var categorySingle = result[i];
var resultJson = {
_id : categorySingle._id,
category_name : categorySingle.category_name,
created_on : categorySingle.created_on,
book_count : 0
}
BookDao.getActiveBookByCategoryId(categorySingle._id, (bookResult) => {
if(bookResult) {
if(bookResult.length > 0) {
resultJson.book_count = bookResult.length;
}
}
});
categoryArray.push(resultJson);
}
callback(categoryArray);
}
});
}
bookDao.js
module.exports.getActiveBookByCategoryId = (categoryId, callback) => {
Book.find({
is_delete : false,
category : categoryId
}, (error, result) => {
if(error) {
console.log(error);
callback(commonUtil.ERROR);
}
if(result) {
callback(result);
}
});
}
Try this, In your code categoryArray.push(resultJson); will not wait for BookDao.getActiveBookByCategoryId to finish because of async behavior.
module.exports.getActiveBookByCategoryId = (categoryId) => {
return Book.count({
is_delete: false,
category: categoryId
});
}
module.exports.getAllActiveCategory = async () => {
try {
// Find all category
const result = await Category.find({
is_delete: false
});
// Create array of promise
const promises = result.map(categorySingle => BookDao.getActiveBookByCategoryId(categorySingle._id));
// Get array of Category count
const data = await Promise.all(promises);
// update count in result
return result.map((categorySingle, i) => {
categorySingle.book_count = data[i];
return categorySingle;
});
} catch (error) {
console.log(error);
}
}
I want to reward a user when he undertakes an action. It can happen the path to his 'coins' does not exists yet. That is why I get the error:
Transaction failure: Error: The data for XXX does not exist.
How can I run a transaction while the path can not exist yet? This is what I tried:
exports.facebookShared = functions.firestore.document('facebookShared/{randomUID}').onCreate(event => {
const data = event.data.data()
const uid = data.uid
var promises = []
promises.push(
db.collection('facebookShared').doc(event.data.id).delete()
)
const pathToCoins = db.collection('users').doc(uid).collection('server').doc('server')
promises.push(
db.runTransaction(t => {
return t.get(pathToCoins)
.then(doc => {
var newCoins = 0
if (doc.data().hasOwnProperty("coins")){
newCoins = doc.data().coins + awardFacebookShare.coins
}
t.update(pathToCoins, { coins: newCoins });
});
})
.then(result => {
console.log('Transaction success', result);
})
.catch(err => {
console.log('Transaction failure:', err);
})
)
return Promise.all(promises)
})
I came across this docs: https://cloud.google.com/nodejs/docs/reference/firestore/0.8.x/Firestore#runTransaction
That docs are better than here: https://firebase.google.com/docs/firestore/manage-data/transactions
Below code works:
exports.facebookShared = functions.firestore.document('facebookShared/{randomUID}').onCreate(event => {
const data = event.data.data()
const uid = data.uid
var promises = []
promises.push(
db.collection('facebookShared').doc(event.data.id).delete()
)
const pathToCoins = db.collection('users').doc(uid).collection('server').doc('server')
promises.push(
db.runTransaction(t => {
return t.get(pathToCoins)
.then(doc => {
var newCoins = awardFacebookShare.coins
if (doc.exists){
if (doc.data().hasOwnProperty("coins")){
newCoins += doc.data().coins
}
t.update(pathToCoins, { coins: newCoins });
return Promise.resolve(newCoins);
}else{
t.create(pathToCoins, { coins: newCoins });
return Promise.resolve(newCoins);
}
});
})
.then(result => {
console.log('Transaction success', result);
})
.catch(err => {
console.log('Transaction failure:', err);
})
)
return Promise.all(promises)
})
I believe my promises aren't being finished because I'm not handling them correctly. At the end of my code, within Promise.all(), console.log(payload) is displaying {}. When it should display something like this:
{
project1: {
description: '...',
stats: {python: 50, css: 50}
},
project2: {
description: '...',
stats: {python: 25, css: 75}
},
project3: {
description: '...',
stats: {python: 10, css: 90}
}
}
code:
app.get("/github", (req, res) => {
const authorizationHeader = {headers: {Authorization: 'Basic ' + keys.github.accessToken}};
const user = 'liondancer';
const githubEndpoint = 'api.github.com/repos/';
var payload = {};
let promises = req.query.projects.map(project => {
let datum = {};
const githubAPIUrl = path.join(githubEndpoint, user, project);
return fetch('https://' + githubAPIUrl + '/languages', authorizationHeader).then(res => {
// Get Languages of a project
if (!isStatus2XX(res)) {
throw 'Status code not 2XX:' + res.status;
}
return res.json();
}).then(res => {
let languagePercentages = {};
let total = 0;
// get total
Object.keys(res).forEach(key => {
total += Number.parseInt(res[key]);
});
// compute percentages
Object.keys(res).forEach(key => {
languagePercentages[key] = (Number.parseInt(res[key]) / total * 100).toFixed(1);
});
datum.stats = languagePercentages;
// Get description of a project
fetch('https://' + githubAPIUrl).then(res => {
if (!isStatus2XX(res)) {
throw 'Status code not 2XX: ' + res.status;
}
return res.json();
}).then(res => {
datum.description = res.description;
payload[project] = datum;
});
}).catch(err => {
console.log('Github API error: ' + err);
});
});
Promise.all(promises).then(() => {
console.log(payload);
res.send(payload);
}).catch(err => {
console.log('nothing ever works...: ' + err);
});
});
At first I replaced .map with .forEach() to have the code execute and the code seemed to have worked properly. payload had the values I expected. However, now that I want to send the aggregated results, I cant seem the properly execute the promises in the correct order or if at all.
just change this line
fetch('https://' + githubAPIUrl).then(res => {
into this
return fetch('https://' + githubAPIUrl).then(res => {
so promise.all will resolve after all nested promises have resolved so payload filled up.