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Node.js constant is not waiting for response from async function

I am new to async/await and I'm trying to set a 'user'-constant as the return value of a MySQL query in Node.js. However, the constant does not wait for the return value of the function. How do I use async and await to set 'user' to the return value of the SQL query?
// Should return a user object
const getUserByUsername = async (username, db) => {
const QUERY = `SELECT * FROM ${table_name} WHERE username = '${username}'`;
const user = await db.query(QUERY,
async (err, result) => {
if (!err) {
console.log("name in SQL function: " + result[0].username);
return await result[0];
} else {
console.log(err);
}
}
);
return user;
};
// Does stuff with the user object
const authenticateUser = async (username, password, done) => {
const user = await getUserByUsername(username, db);
console.log("name in main function: " + user.username);
// Trying to do stuff with the user object...
}
What I get in the terminal:
name in main function: undefined
UnhandledPromiseRejectionWarning: Error: data and hash arguments required
at Object.compare
at /app/node_modules/bcrypt/promises.js:29:12
at new Promise (<anonymous>)
at Object.module.exports.promise
etc.....
name in SQL function: john

When you use db.query with a callback, it does not return a promise
Try the following code instead
const getUserByUsername = async (username, db) => {
const QUERY = `SELECT * FROM ${table_name} WHERE username = '${username}'`;
const result = await db.query(QUERY);
console.log("name in SQL function: " + result[0].username);
return result[0];
};

Please try the below code.
const getUserByUsername = async (username, db) => {
try {
const QUERY = `SELECT * FROM ${table_name} WHERE username = '${username}'`;
const user = await db.query(QUERY, async (err, result) => {
if (err) {
throw err;
}
if (result && result.length) {
return result[0];
}
throw new Error(`User with username ${username} not found`);
});
console.log(`name in SQL function: ${user.username}`);
return user;
} catch (error) {
console.log(error);
throw error;
}
};

After jfriend00's comment, I decided to make my function a callback function. I found this answer explaining how to do it: https://stackoverflow.com/a/31875808/6817961. This worked!
My code now:
// Function returns a user object
const getUserByUsername = (username, callback) => {
const QUERY = `SELECT * FROM ${db_name} WHERE username = '${username}'`;
db.query(QUERY, (err, result) => {
if (!err) {
if (result.length > 0) {
return callback(null, result[0]);
} else {
err = "No user with that username";
return callback(err, null);
}
} else {
return callback(err, null);
}
});
};
// Then this function does stuff with the callback
const authenticateUser = (username, password, done) => {
getUserByUsername(username, async (err, result) => {
if (err) {
console.log(err);
return done(null, false, { message: err });
} else {
const user = result;
// result will now return the user object!

Return value from callback in TypeScript [duplicate]

This question already has answers here:
How do I return the response from an asynchronous call?
(41 answers)
Closed 3 years ago.
I have a function in typescrypt in file Service.ts:
export const doCallAuth = (username, password) => {
var auth = new Auth({
url: '...',
});
var status;
auth.authenticate(username, password, function (err, user) {
if (err) {
console.log(err);
status = 'no';
} else if (!user.uid) {
console.log("user not found Error");
status = 'no';
} else if (user.uid) {
console.log("success : user " + user.uid + " found ");
status = 'yes';
}
});
return status;
}
I call this method by :
var result = Service.doCallAuth('test', 'test');
And variable result is undefined
I don't know why result is undefined
Can anybody help me out ?
Thanks in advance. :)

You can use Promise or callback patterns
1. Promise
export const doCallAuth = (username, password) => {
return new Promise((resolve, reject) => {
var auth = new Auth({ url: "..." });
auth.authenticate(username, password, (err, user) => {
if (err) {
reject(err);
} else if (!user.uid) {
reject(new Error("user not found Error"));
} else if (user.uid) {
console.log("success : user " + user.uid + " found ");
resolve(user);
}
});
});
};
Service.doCallAuth("test", "test")
.then(user => {
console.log("success : user " + user.uid + " found ");
})
.catch(e => {
console.log(e);
});
2. Callback
export const doCallAuthCallBack = (username, password, callback) => {
var auth = new Auth({ url: "..." });
auth.authenticate(username, password, (err, user) => {
if (err) {
callback(err);
} else if (!user.uid) {
callback(new Error("user not found Error"));
} else if (user.uid) {
callback(null, user);
}
});
};
Service.doCallAuthCallBack("test", "test", (err, user) => {
if (err) {
console.log(err);
} else {
console.log("success : user " + user.uid + " found ");
}
});

Try this one.
export const doCallAuth = (username, password, callback) => {
var auth = new Auth({
url: '...',
});
var status;
auth.authenticate(username, password, callback);
}
var result;
Service.doCallAuth('test', 'test', function (err, user) {
if (err) {
console.log(err);
status = 'no';
} else if (!user.uid) {
console.log("user not found Error");
status = 'no';
} else if (user.uid) {
console.log("success : user " + user.uid + " found ");
status = 'yes';
}
result = status;
});

To get value from AJAX call need to Use async and await
export const doCallAuth = async function(username, password) => {
var auth = new Auth({
url: '...',
});
var status;
auth.authenticate(username, password, function (err, user) {
if (err) {
console.log(err);
status = 'no';
} else if (!user.uid) {
console.log("user not found Error");
status = 'no';
} else if (user.uid) {
console.log("success : user " + user.uid + " found ");
status = 'yes';
}
return status;
});
}
call this method by :
var result = await Service.doCallAuth('test', 'test');

Async / await in node nested functions?

I'm trying to get async / await to trigger events in order, but it seems I'm missing something as my console.log markers are triggering in reverse to the order I was hoping for.
I 'm wondering if is to do with my use of nested functions in users.js but having tried multiple variations of async / await, it consistently doesn't work as expected.
// index.js
var users = require("./users.js");
app.post("/getToken", async function(req, res) {
if (req.body.email && req.body.password) {
const email = req.body.email;
const password = req.body.password;
const user = await users(email, password)
// running this should output console.log("No 1")
// from users.js first, but doesn't ?
console.log('No 2')
if (user) {
var payload = {
id: user.id
};
var token = jwt.encode(payload, cfg.jwtSecret);
res.json({
token: token
});
} else {
res.sendStatus(401);
}
} else {
res.sendStatus(401);
}
});
// users.js
module.exports = function(emailAddress, password) {
db.connect();
var query = `
SELECT
id,
email,
password,
salt
FROM
users
WHERE
email = ?`;
var query_params = [emailAddress];
db.query(
query,
query_params,
function(error, result, fields) {
console.log('No 1')
if (error) throw error;
if ( result.length == 1 ) {
if ( checkPass(password, result[0].password, result[0].salt ) ) {
return { id: result[0].id }
} else {
console.log("login False | Password");
return false;
}
} else {
console.log("login False | username");
return false;
}
}
)
}

Your users.js function doesn't return anything. The callbacks you're passing query do, but the overall function doesn't. Since it never returns anything explicitly, the result of calling it is undefined. If you await undefined, it's like await Promise.resolve(undefined) and so your resolution handler is called quite quickly.
You want that function to return a promise that doesn't get resolved until the work is done. Since what it uses is an old-style Node callbck API, it's reasonable to use new Promise to create that promise (alternately, get or create a promise-enabled API to that DB).
I also suspect you're calling connect incorrectly, since normally that would be an asynchronous action, but you're treating it as though it were synchronous.
See comments:
users.js
module.exports = function(emailAddress, password) {
return new Promise((resolve, reject) => {
// Use the callback to know when the connection is established
db.connect(error => {
if (error) {
// Connection failed
reject(error);
return;
}
var query = `
SELECT
id,
email,
password,
salt
FROM
users
WHERE
email = ?`;
var query_params = [emailAddress];
db.query(
query,
query_params,
function(error, result, fields) {
// Throwing an error here does nothing useful. Instead,
// reject the promise.
if (error) {
reject(error);
return;
}
// Resolve our promise based on what we got
if ( result.length == 1 ) {
if ( checkPass(password, result[0].password, result[0].salt ) ) {
resolve({ id: result[0].id });
} else {
console.log("login False | Password");
resolve(false);
}
} else {
console.log("login False | username");
resolve(false);
}
}
);
});
});
}
Then using it:
app.post("/getToken", async function(req, res) {
// You must handle errors, since `post` won't do anything with the return
// value of this function
try {
if (req.body.email && req.body.password) {
const email = req.body.email;
const password = req.body.password;
// Now this waits here, since `users` returns a promise that
// isn't resolved until the query completes
const user = await users(email, password)
console.log('No 2')
if (user) {
var payload = {
id: user.id
};
var token = jwt.encode(payload, cfg.jwtSecret);
res.json({
token: token
});
} else {
res.sendStatus(401);
}
} else {
res.sendStatus(401);
}
} catch (e) {
res.sendStatus(401);
}
});

The problem is that db.query function is asynchronous - you are providing callback function that is executed when database call is finished. You probably need to wrap this whole function in Promise:
module.exports = function(emailAddress, password) {
return new Promise(function(resolve, reject) {
db.connect();
var query = `
SELECT
id,
email,
password,
salt
FROM
users
WHERE
email = ?`;
var query_params = [emailAddress];
db.query(
query,
query_params,
function(error, result, fields) {
if (error) return reject(error)
if ( result.length == 1 ) {
if ( checkPass(password, result[0].password, result[0].salt ) ) {
resolve({id: result[0].id})
} else {
console.log("login False | Password");
reject();
}
} else {
console.log("login False | username");
reject();
}
}
)
})
}
You can learn more about Promise API here
EDIT:
So you should additionally make connect synchronous. Here's a piece of code I have refactored for you. It should work just fine. I have used some ES6 elements to make it more readable.
const connect = () => new Promise((resolve, reject) => {
db.connect((err) => {
if (err) return reject(err);
resolve();
})
})
const makeDbRequest = (emailAddress, password) => new Promise((resolve, reject) => {
const query = `
SELECT
id,
email,
password,
salt
FROM
users
WHERE
email = ?`;
const query_params = [emailAddress];
db.query(
query,
query_params,
handleDbData(resolve, reject, password),
);
})
const handleDbData = (resolve, reject, password) => (error, result, fields) => {
if (error) return reject(error)
if ( result.length == 1 ) {
if ( checkPass(password, result[0].password, result[0].salt ) ) {
resolve({id: result[0].id})
} else {
console.log("login False | Password");
reject();
}
} else {
console.log("login False | username");
reject();
}
}
module.exports = (emailAddress, password) => new Promise((resolve, reject) => {
connect()
.then(() => {
makeDbRequest(emailAddress, password)
.then(resolve)
.catch(reject)
})
.catch(reject);
})

Again about async/await in javascript

My function looks like this now:
var GetImages = async() => {
var images_array = [];
await request ({
url: `https://api.tumblr.com/v2/blog/nameblog/posts?api_key=${process.env.TUMBLR_KEY}&type=photo`,
json: true
}, (error, response, body) => {
if(error){
console.log('Unable to connect');
}else if(body.meta.status === "ZERO_RESULTS"){
console.log('Uable to find that address.');
}else if(body.meta.status === 200){
body.response.posts.forEach(function(obj) {
obj.photos.forEach(function(photo) {
if(photo.original_size.width>photo.original_size.height){
images_array.push(photo.original_size.url);
console.log("dawdaw");
}
});
});
//callback(images_array);
}
});
return images_array;
}
I have no idea, how return my array after i'll fill it with values. With callback it works fine, but i wanna do it with async/await methid in right way. Thank you for help.

create method to return promise for request and use that method with await
requestPromise = () => {
return new Promise(function(resolve, reject) {
request({
url: `https://api.tumblr.com/v2/blog/nameblog/posts?api_key=${process.env.TUMBLR_KEY}&type=photo`,
json: true
}, (error, response, body) => {
if (error) {
console.log('Unable to connect');
reject();
} else if (body.meta.status === "ZERO_RESULTS") {
console.log('Uable to find that address.');
reject();
} else if (body.meta.status === 200) {
body.response.posts.forEach(function(obj) {
obj.photos.forEach(function(photo) {
if (photo.original_size.width > photo.original_size.height) {
images_array.push(photo.original_size.url);
console.log("dawdaw");
}
});
});
resolve(images_array)
}
});
});
}
var GetImages = async() => {
try
{
images = await requestPromise();
return images;
}
catch(e){return [];}
}

Mutable variable is accessible from closure with promise and loop

I use the following code to generate a unique token for a user. Data for users is stored on MongoDB so I use promise to handle asynchronous talking to the db. In WebStorm I receive this warning : Mutable variable is accessible from closure with promise and loop. and I know there have been posts on SO about this thing, but I my case is more complicated. I know I may not even need to worry about it as I only use the last value of token but what I want to solve this issue in a correct way ?
var generateToken = function(userId) {
User.findOne({userId: userId}, function(err, user) {
if (user !== null) {
var loop = true;
while (loop) {
var token = Common.randomGenerator(20);
User.find({tokens: token}, function(err, result) {
if (err) {
loop = false;
return Promise.reject('Error querying the database');
} else {
if (result.length === 0) {
if (user.tokens === undefined){
user.tokens.push(token);
}
loop = false;
return Promise.resolve(token);
}
}
});
}
} else {
return Promise.reject('UserNotFound');
}
});
};
I came up with the following solution , is it correct ?
var generateToken = function(userId) {
User.findOne({userId: userId}, function(err, user) {
if (user !== null) {
var loop = true;
while (loop) {
var token = Common.randomGenerator(20);
(function(e){
User.find({tokens: e}, function(err, result) {
if (err) {
return Promise.reject('Error querying the database');
} else {
if (result.length === 0) {
if (user.tokens === undefined){
user.tokens = [];
}
user.tokens.push(e)
return Promise.resolve(e);
}
}
});
})(token);
}
} else {
return Promise.reject('UserNotFound');
}
});
};
NOTE As #Alex Nikulin suggested , I flipped loop to false before sending back the result of the promise. But still it's an infinite loop as it doesn't go into the User.find({tokens: e})....

Your problem is that, return statement is within function, not within loop.Your loop is infinite. I has decomposited your code.Or simply make loop false, when you resolve/reject promise. Also my code will wait each answer from User, and error will gone. And your variant with wrap function is correct (function(e){})(token).
var generateToken = function(userId) {
return new Promise(function(resolve, reject) {
User.findOne({userId: userId}, function(err, user) {
if (user !== null) {
userTokenIterator(user,resolve, reject);
} else {
reject('UserNotFound');
}
});
});
};
var addTokenToUser = function(token,user){
return new Promise(function(resolve, reject) {
User.find({tokens: token}, function(err, result) {
if (err) {
reject('Error querying the database');
} else {
var result = result.length === 0;
if (result) {
if(!user.tokens) {
user.tokens = []
}
user.tokens.push(token);
}
resolve(result);
}
});
});
};
var userTokenIterator = function (user, resolve, reject){
var token = Common.randomGenerator(20);
addTokenToUser(token, user).then(function(result){
if(result) {
resolve(token);
}else{
userTokenIterator(user,resolve, reject)
}
},function(error){
reject(error);
});
};