We Keep Coding

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client error occured while using redirect in nodejs

I am making a project where I am facing this error. What I wanted to do is that according to the condition it should redirect the server to the particular routes but getting this error.
routes.post("/check", (req, res) => {
console.log("/check");
// console.log(req.body);
username = req.body.username;
password = req.body.password;
console.log("Step 1");
console.log("Username:", username, "\n", "Password", password);
console.log(public);
for (let i in public) {
if (username === i && password === public[i]) {
console.log("Authenticated success");
res.redirect("/public");
} else {
res.redirect("/404");
}
}
res.redirect("/public");
});
Output is
/check
Step 1
Username: shivam2
Password 4321
{ shivam2: '4321', arjun2: 'dcba' }
Authenticated success
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client

You should return in case of successful authentication:
routes.post("/check", (req, res) => {
console.log("/check");
// console.log(req.body);
username = req.body.username;
password = req.body.password;
console.log("Step 1");
console.log("Username:", username, "\n", "Password", password);
console.log(public);
for (let i in public) {
if (username === i && password === public[i]) {
console.log("Authenticated success");
return res.redirect("/public");
}
}
res.redirect("/404");
});

You're calling multiple redirects, one in each iteration of the loop, which causes the error. However, you don't need the loop at all - you can examine public[username] directly (logging removed for brevity's sake):
routes.post("/check", (req, res) => {
username = req.body.username;
password = req.body.password;
if (public[username] === password) {
console.log("Authenticated success");
res.redirect("/public");
} else {
res.redirect("/404");
}
});

Condition if/else don't work like expected in nodejs

I'm creating a simple api witch verify if the username and/or password are in the DB and if they are correct.
When I post correct data, it works. When I post a wrong password, it also works. But when I post a wrong username, my condition don't jump to the else. If the username is wrong, it means it is not in the DB. But here, it is like if it was in the DB, but he is not, so I get an error : " TypeError: Cannot read properties of undefined (reading 'Username') "
Here the code
app.post('/login', function(req, res) {
(async () => {
const bcrypt = require('bcrypt')
try {
username = req.query.username
password = req.query.password
let salt = await bcrypt.genSalt(10)
let hash = await bcrypt.hash(password, salt)
db_conn.getConnection( (err, conn) => {
if(err) throw err;
conn.query("SELECT * FROM mod803_appusers WHERE Username=? ", [username], (err, rows) => {
//Problem here : when I put a wrong password, it's ok, this condition works because there is a password, and if bcrypt.compare is true, it sends response, but if it's false, it sends 'Wrong password'.
//But if the Username is Wrong, it means there is no username in the DB. So here, I want this condition jump to the else : 'Incorrect username' but it doesn't.
if(rows[0]['Username'] && rows[0]['Password']) {
bcrypt.compare(password, rows[0]['Password'], function(err, result) {
if(result){
res.send({"table": rows});
} else {
res.send("Wrong password");
}});
} else {
res.send('Incorrect username');
}
})
})
} catch (error) {
console.log(error.message)
}
})()
})
Thanks

Cannot set headers after they are sent to the client using nodejs mysql

What I am attempting to do is write a statement to check if email exists in my mysql database when a user registers. In postman it sends me the correct error message of "user already taken" however the server crashes after and displays "cannot set headers after they are sent to the client." I have read similar posts but did not help.
//The following code is in my user.service.js file:
const pool = require("../../config/database");
module.exports = {
//Create new user
createUser: (data, callBack) =>{
pool.query(
`insert into registration(name, email, password, confirm_password)
values(?,?,?,?)`,
[
data.name,
data.email,
data.password,
data.confirm_password
],
(error, results, fields) =>{
if(error){
return callBack(error);
}
return callBack(null, results);
}
);
}
}
//The following code is in my user.controller.js file:
const {
createUser,
} = require("./user.service");
const pool = require("../../config/database");
module.exports = {
createUser: (req, res) =>{
const body = req.body;
const salt = genSaltSync(10);
pool.query('SELECT email FROM registration WHERE email = ?', [body.email], (error, results) =>{
if(error){
console.log(error);
}
if(results.length > 0){
return res.status(400).json({
message: 'User already taken'
})
}
})
createUser(body, (err, results) => {
if(err){
console.log(err);
return res.status(500).json({
success:0,
message:"Error in database connection"
});
}
return res.status(200).json({
success: 1,
message: `User ${results.insertId} signed up successfully`,
data: results
});
});
}
}
//The following code is from user.router.js file:
const {
createUser,
} = require("./user.controller");
const router = require("express").Router();
router.post("/signup", createUser);
module.exports = router;

In your createUser function that is executed on the post request you are doing two things. First you check whether a user with the provided email exists and, second, you create a user. However, those functions are not executed consecutively, instead they are running simultaneously and thus create a race condition.
So going off on your example, if the email check query SELECT email FROM registration WHERE email = ? is faster and the user already exists, it will respond with:
return res.status(400).json({
message: 'User already taken'
})
but the createUser function (below) is still running and once it is finished, it will try to also send a response. Therefore, you are presented with an application crash in the console even though in the postman you can see the response stating that the user already exists.
In order to fix this error you should execute the createUser function only if the results.length is 0 inside the callback provided to the email check query, like so:
createUser: (req, res) => {
const body = req.body;
const salt = genSaltSync(10);
pool.query('SELECT email FROM registration WHERE email = ?', [body.email], (error, results) =>{
if(error){
console.log(error);
}
if(results.length > 0){
return res.status(400).json({
message: 'User already taken'
})
}
createUser(body, (err, results) => {
if(err){
console.log(err);
return res.status(500).json({
success:0,
message:"Error in database connection"
});
}
return res.status(200).json({
success: 1,
message: `User ${results.insertId} signed up successfully`,
data: results
});
});
})
}
Now you execute the createUser function only if a user with the provided email doesn't exist, which effectively removes the race condition between the two functions.

sessions are not getting stored in the browser cookies

When i trying to run my API in postman it is working fine and sessions are getting maintained. But when i am trying to run it from UI Part the login session is not working.
This is my Login API from where i am login into
app.post('/user/login', (req, res, next) => {
const body = req.body;
let email = body.email;
let password = body.password;
const userDetails = db.collection(userProfiles);
userDetails.findOne({email: email}, function (err, user) {
if (err) {
return next(err);
} else if (!user) {
return res.status(400).send({
status: 'error',
message: 'user does not exist'
});
} else {
if (user.password == password) {
user_object = user;
req.session.user = user;
return res.send({
user_obj: user,
status: 'success',
message: 'Successfully logged in'
});
} else {
return res.status(400).send({
status: 'error',
message: 'Wrong Password'
})
}
}
return res.send(user);
});
});
This is my session API from where i am sending user req.session.user on calling this api
app.get('/user/dashboard', function (req, res) {
if (!req.session.user) {
return res.status(400).send({
data:'need to be logged in'
});
}
return res.status(200).send({
data:req.session.user
});
});```
The below is the javascript file from where i am trying to call the user stores in req.session.user
`
async function fetchUserId(){
let cookie = document.cookie;
let res = await fetch('http://127.0.0.1:8080/user/dashboard',
{redirect: 'follow',
headers:{
"Cookie":cookie
}});
let userJson = await res.json();
console.log(res);
console.log(userJson);
//return userJson;
};
`
when i hit the login API from Postman it is maintaining session and working fine but when i do the same from UI from browser it is giving error status 400 every time.

You can do a
fetch(url, options).then(function(res) { console.log(res} )
and
app.get('/user/dashboard', function (req, res) {
console.log(req.headers)
if (!req.session.user) {
return res.status(400).send({
data:'need to be logged in'
});
}
return res.status(200).send({
data:req.session.user
});
});
To check is the cookie really there and where is the user object.
And you can check your browsers dev console to see if the cookie is updating.
I see that is fetch request you put a cookie in your header. But than at the API you are looking for a user at req.session.user. Although the cookie is in req.header["Cookie"].

Update user information

Tried this for updating user information , only phone number but it's not getting update.
router.post('/edit', checkAuth, function (req, res, next) {
console.log(req.userData.userId)
User.update({_id: req.userData.userId}, {$set:req.userData.phoneNo}, function (err){
if (err) {
console.log(err);
}
res.status(200).send(req.userData);
});
});
My user controller const mongoose = require ('mongoose');
const User = mongoose.model('User');
module.exports.register = (req, res, next) =>{
var user = new User();
user.fullName = req.body.fullName;
user.email = req.body.email;
user.password = req.body.password;
user.phoneNumber = req.body.phoneNumber;
user.save((err, doc) =>{
if(!err)
res.send(doc);
else{
if (err.code == 11000)
res.status(422).send(["Entered duplicate email address. Please check"]);
else
return next(err);
}
});
}
And then I am authenticating by passing jwt on this field
phoneNo: user[0].phoneNumber
The auth-token verifies and decode the fields
const token = req.headers.authorization.split(" ")[1];
const decoded = jwt.verify(token, process.env.JWT_KEY)
req.userData = decoded;
Update is not working and getting error message Invalid atomic update value for $set. Expected an object, received string .

first of all, you should use PATCH-method - because you are updating only one item in existed object, in body you should send id of user and new value of certain value. If you use mongoose you can try it
User.findOneAndUpdate({ _id: id }, updatedItem, { new: true }, (err, doc) => {
if (err) return res.send(err.message)
if (doc) return res.send(doc);
})
const id = req.body._id;, if you dont use mongoose you should try findAndModify method

Your code
User.update({_id: req.userData.userId}, {$set:req.userData.phoneNo}
Correct code:
User.update({_id: req.userData.userId}, {$set:{phoneNumber:req.userData.phoneNo}}
Try this method:
User.findByIdAndUpdate(req.userData.userId, { $set:{phoneNumber:req.userData.phoneNo}}, { new: true }, function (err, user) {
if (err) console.log(err);
res.send(user);
});