I am getting this error : Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client - mongodb

Question

When I am sending POST Request for Login, then show this Error. I have used mongoose & MongoDB Atlas.
If I send POST request with valid email & password, it also shows this error.
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent
to the client
But POST request for registration is working well.
User Model
const mongoose = require('mongoose')
const Schema = mongoose.Schema
const userSchema = new Schema({
name: {
type: String,
required: true,
trim: true
},
email: {
type: String,
required: true,
},
password: {
type: String,
required: true
},
balance: Number,
income: Number,
expense: Number,
transactions: {
type: [{
type: Schema.Types.ObjectId,
ref: 'Transaction'
}]
}
})
const User = mongoose.model('User', userSchema)
module.exports = User
User Controller
const registorValidate = require('../validator/registrationValidate')
const User = require('../models/userModel')
const bcrypt = require('bcrypt')
const loginValidate = require('../validator/loginValidator')
const jwt = require('jsonwebtoken')
module.exports = {
login: (req, res) => {
const { email, password } = req.body
let logValidate = loginValidate({ email, password })
if (!logValidate.isValid) {
res.status(400).json(logValidate.error)
return
}
User.findOne({ email })
.then(user => {
if (!user) {
console.log(`${email} not found`)
res.json({
msg: `${email} not found`
})
}
bcrypt.compare(password, user.password, (err, result) => {
if (err) {
res.status(400).json({
msg: 'Error occured'
})
}
if (!result) {
res.status(404).json({
msg: `Password doesn't match`
})
}
let token = jwt.sign({
_id: user._id,
name: user.name,
email: user.email
}, 'SECRET', { expiresIn: '2h' })
res.status(200).json({
msg: 'Login successful',
token: `Bearer ${token}`
})
})
return
})
.catch(err => {
res.status(500).json({
msg: 'Error occured'
})
})
res.end()
},
registration: (req, res) => {
let { name, email, password, confirmPassword } = req.body
let validate = registorValidate({ name, email, password, confirmPassword })
if (!validate.isValid) {
res.status(400).json(validate.error)
} else {
User.findOne({ email })
.then(user => {
if (user) {
res.json({
msg: `${email} is already exist`
})
} else {
bcrypt.hash(password, 11, (err, hash) => {
if (err) {
res.status(500).json({
msg: 'Server error occured'
})
}
let user = new User({
name,
email,
password: hash
})
user.save()
.then(user => {
res.status(201).json({
msg: `Thanks ${name} for your registration`,
user
})
})
.catch(err => {
res.status(500).json({
msg: 'Error occured'
})
})
})
}
})
.catch(err => {
res.status(500).json({
msg: 'Error occured'
})
})
}
}
}
Login Validator
const validator = require('validator')
const validate = user => {
let error = {}
// Email validator
if (!user.email) {
error.email = 'Please provide an Email'
} else if (!validator.isEmail(user.email)) {
error.email = 'Please provide a valid Email'
}
// Password validate
if (!user.password) {
error.password = 'Please provide a password'
} else if (user.password.length < 6) {
error.password = 'Password Must be greater or Equal to 6 characters'
}
return {
error,
isValid: Object.keys(error).length === 0
}
}
module.exports = validate
Thanks.

Answer 1

You don't need to put res.end() because when you called res.json() earlier, it already sent the response.
Please be advised that you should return when you call res.end(), res.send(), 'res.json()' and other operations that send the response, just like what you did with res.status(400).json(logValidate.error)
This should be one of the ways prevent you from getting ERR_HTTP_HEADERS_SENT, but keep in mind that if you have nested callbacks, you should return from the outer scope as well