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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!

Unable to access user info object property - facebook chat api

I'm using Facebook chat api to create a simple cli script that will reply to messages that are sent to my facebook account. I'm trying to assign and get the user name and my name to use them inside the reply but they are always undefined. I think that the object property aren't assigned correctly. Is there a fix for this?
require('dotenv').config();
const fs = require('fs');
const fb = require('facebook-chat-api');
const path = require('path');
const appStateFile = path.format({ dir: __dirname, base: 'appstate.json' });
let currentUser = null;
if( !fs.existsSync(appStateFile) ){
//debug .env
console.log(process.env);
fb({email: process.env.FB_EMAIL, password: process.env.FB_PWD}, (err, api) => {
if(err){
return console.log(err);
}
console.log(api);
api.setOptions({
listenEvents: true
});
fs.writeFileSync(appStateFile, JSON.stringify(api.getAppState()));
let id = api.getCurrentUserID();
api.getUserInfo(id, (err, profile) => {
console.log(profile); // profile is logged correctly
currentUser = profile;
});
api.listenMqtt( (err, event) => {
if(err){
return console.log(err);
}
if(event.type === 'message'){
console.log(event.body)
api.getUserInfo(event.senderID, (err, user) => {
if(err){
return console.log(err);
}
console.log(user); // user object is logged correctly
api.sendMessage('...', event.threadID)
});
}
});
});
}else{
fb({appState: JSON.parse(fs.readFileSync(appStateFile))}, (err, api) => {
if(err){
return console.log(err);
}
console.log(api);
api.setOptions({
listenEvents: true
});
let id = api.getCurrentUserID();
api.getUserInfo(id, (err, profile) => {
console.log(profile);
currentUser = profile;
});
api.listenMqtt( (err, event) => {
if(err){
return console.log(err);
}
if(event.type === 'message'){
console.log(event.body)
api.getUserInfo(event.senderID, (err, user) => {
if(err){
return console.log(err);
}
console.log(user)
api.sendMessage(`FB Pager v1.0.\nHi ${user.name}!Your message was forwarded with an email to ${currentUser.name}.`, event.threadID)
});
}
});
});
}

I think the problem here is that api.getUserInfo is asynchronous.
So you would need to nest them to get it to work.
Or you can try this, since getUSerInfo allows you to add an array of user ids to get the data for:
api.listenMqtt((err, event) => {
if (err) {
return console.log(err);
}
if (event.type === "message") {
const currentUserId = api.getCurrentUserID();
const senderId = event.senderID;
api.getUserInfo([currentUserId, senderId], (err, ret) => {
if(err) return console.error(err);
// Ret should contain the two users
// See: https://github.com/Schmavery/facebook-chat-api/blob/master/DOCS.md#getUserInfo
console.log(ret);
});
}
});
Nesting user calls method:
api.listenMqtt((err, event) => {
if (err) {
return console.log(err);
}
if (event.type === "message") {
let currentUserId = api.getCurrentUserID();
api.getUserInfo(currentUserId, (err1, signedInUser) => {
if (err1) {
return console.log(err);
}
api.getUserInfo(event.senderID, (err2, userInMessage) => {
if (err2) {
return console.log(err);
}
console.log(signedInUser, userInMessage)
api.sendMessage("...", event.threadID);
});
});
}
});

After a lot of debug I've found the correct way to access the needed informations. Since the user informations after that are retrived are mapped to another object that is the userId, the only way to access to each property is to use a for loop. Initially I was thinking that this can be avoided but unfortunately it's necessary otherwise using only dot notation will result in undefined. This is how I've solved
api.getUserInfo(userId, (err, user) => {
let username;
if(err){
return console.log(err);
}
for(var prop in user){
username = user[prop].name;
}
api.sendMessage(`Hello ${username!}`, event.threadID);
});

Passing a variable from ReactJS frontend to NodeJS back end using a GET route

I am working on a react app and am trying to find a way to pass a variable I define in my front-end (Question.js) to my back-end (server.js) so that I can issue different queries. I have the code
//Question.js
state = {
data: null
};
componentDidMount() {
this.callBackendAPI()
.then(res => this.setState({ data: res.express }))
.catch(err => console.log(err));
}
callBackendAPI = async () => {
const response = await fetch('/express_backend');
const body = await response.json();
if (response.status !== 200) {
throw Error(body.message)
}
return body;
};
//server.js
con.connect(function (err) {
if (err) throw err;
con.query("SELECT question FROM s1questions WHERE ID = 1", function (err, result, fields) {
if (err) throw err;
app.get('/express_backend', (req, res) => {
var x = JSON.stringify(result[0].question);
res.send({ express: `${x}` });
});
});
});

Your sever should probably split your database connection from your route handler definitions. Also, you could use query parameters to access questions based on their id in the database.
// question.js
callBackendAPI = async () => {
const response = await fetch(`/express_backend?questionId=1`);
const body = await response.json();
if (response.status !== 200) {
throw Error(body.message)
}
return body;
};
// server.js
app.get('/express_backend', (req, res) => {
const { questionId } = req.query;
// query database for question by id
});

Why is rows(callback) function from db.all returning undefined while rows is defined?

I'm calling a function to see if an email adress is in the db. It's either an empty or filled array. Whenever i return this value it is undefined afterwards. How can I solve this? Thanks in advance!
I have tried using next() and promises.
The function that calls the db query function.
const emailExists = async function(req,res,next){
let emailInDb = await usermodel.getOneByEmail(req, next);
console.log(emailInDb);
if(emailInDb.length !==0){
res.send('email already in use!');
}
else{
return next();
}
};
The db query.
const getOneByEmail = function (req, next){
let db = new sqlite3.Database(dbPath, (err) => {
if (err) {
console.error(err.message);
}
console.log('Connected to books db.');
});
db.all(`SELECT * FROM users WHERE email = ?`, [req.body.email],
(err, rows) => {
console.log(rows);
return rows;
});
};
console.log(emailInDb) gives undefined.
While console.log(rows) gives an array with results.

Putting await in front of a non async function does not magically make the function wait for the db-calls to resolve. You need to wrap the db-calls in a promise, e.g:
const getOneByEmail = (req, next) => {
return new Promise((resolve, reject) => {
let db = new sqlite3.Database(dbPath, (err) => {
if (err) {
console.error(err.message);
reject(err);
}
console.log('Connected to books db.');
});
db.all(`SELECT * FROM users WHERE email = ?`, [req.body.email],
(err, rows) => {
// TODO: check for error here and reject
console.log(rows);
resolve(rows);
});
});
};
Note that you shouldn't connect to the database each time you call getOneByEmail, instead reuse the connection...

how to wait till DB connection is made and queries are executed for each database in an array

A file contains json data with details of database.
For each database connection, a series of queries need to be executed.
Currently, the map function is waiting for the database connection.
Below is the start function
function start() {
console.log('function initiated');
try {
let jsonData = fs.readFileSync('../request.json');
let jsonString = JSON.parse(jsonData);
//jsonString['request'].forEach(async function(json) {
jsonString['request'].map(async json => {
dbdetails = json.dbdetails;
//dbdetails.forEach(async function(db){
await dbbdetails.map(async db => {
console.log('pdbdetails: ' + db);
connString = json.connString;
//makes the DB connection
await connectDB(db.userId, db.Password, connString)
.then(async conn => {
await execution(conn, pdbDetails, vmUser, vmPassword, ip);
})
.catch(err => {
console.log(err);
});
console.log('after each execution');
//}
});
});
} catch (err) {
console.log(err.message);
return;
}
}
Below function is to make a database connection and return the connection
function connectDB(oUser, oPassword, connString) {
console.log('inside connectDB');
return new Promise((resolve, reject) => {
oracledb.getConnection(
{
user: oUser,
password: oPassword,
connectString: connString
},
function(err, connection) {
if (err) {
console.error(err.message);
reject(err);
//throw err;
}
console.log('returning connection');
//console.log(connection);
resolve(connection);
//return connection;
}
);
});
}
below is the function which executes servies of queries on database
function execution() {
/// series of sql query execution
}

Not sure what you’re trying to do exactly, but sounds like the problem is that .map doesn’t wait for your async functions. If you have to do them one at a time, use a for loop:
for ( var item of array ) {
await item.something();
}
To do them all at once:
var results = await Promise.all( array.map( item => item.something() )