node.js - Cannot set headers after they are sent to the client

Question

Cannot set headers after they are sent to the client. This is my back-end side error after authentication post request.It looks like problem with headers. I'm sorry for my dirty code for my project i need to do something else,so there some code in comment. This is my code

const express = require("express");
const router = express.Router();
const Spec = require("../models/specialist");
const jwt = require("jsonwebtoken");
const config = require("../config/data");
const passport = require('passport');
const LocalStrategy = require('passport-local').Strategy;


router.get("/login",(req,res)=>{
    res.render("login");
});
router.get("/signup",(req,res)=>{
    res.render("signup");
});

    //Registration route
router.post("/spec/register",(req,res)=>{
        let date=new Date();
        let newUser = new Spec({
            name:req.body.spec_name,
            email_num:req.body.spec_email,
            password:req.body.spec_password,
            role:"User",
            isActive:true,
            created:date,
            updatedToken:"JWT"

        });
        Spec.addUser(newUser,(err,user)=>{
            if(err){
                console.log("err");
              } else {
                res.header("Content-Type","application/json");
            //    res.redirect("/users/login");

              }
        });


    });

// passport.use(new LocalStrategy(
//     function(username, password, done) {
//      Spec.getUser(username, function(err, user){
//          if(err) return console.error(err.stack);
//          if(!user){
//              return done(null, false, {message: 'Unknown User'});
//          }

//          Spec.comparePassword(password, user.password, function(err, isMatch){
//              if(err) return console.error(err.stack);
//              if(isMatch){
//                  return done(null, user);
//              } else {
//                  return done(null, false, {message: 'Invalid password'});
//              }
//          });
//      });
//     }));

//   passport.serializeUser(function(user, done) {
//     done(null, user.id);
//   });

//   passport.deserializeUser(function(id, done) {
//     User.getUserById(id, function(err, user) {
//       done(err, user);
//     });
//   });

     //Authentication route
router.post('/spec/authenticate', (req, res,next) => {
        const email = req.body.email;
        const password = req.body.password;

        Spec.getUser(email, (err, user) => {
          if(err) throw err;
          if(!user){
            return res.json({success: false, msg: 'User not found'});
          }

          Spec.comparePassword(password, user.password, (err, isMatch) => {
            if(err) throw err;
            if(isMatch){
              let payload={
                name:user.name,
                email:user.email_num,
                role:user.role,
                deleted:user.deleted,
                isActive:user.isActive,
                created:user.created
              };
              let token = jwt.sign(payload,config.JWT_SECRET,{
                  expiresIn:1440
              })

              Spec.saveToken(email,token,(err,success)=>{
                if(err) return err;
                console.log("Success");
                // res.setHeader('Authorization','bearer '+token );
                res.cookie('Authorization','bearer '+token);
                res.json ({ success: true, token: 'bearer ' + token });
                res.redirect("/users/user");
              }); 


            } else {
              return res.json({success: false, msg: 'Wrong password'});
            }
      });
   });
// res.redirect("/user");
 });
router.get("/user",passport.authenticate('jwt',{session:false}), (req,res)=>{

    res.render("user");
});
router.get("/forgotPass",(req,res)=>{
    res.render("forgotPass");
});
router.get("/we",(req,res)=>{
    res.render("we");
});


module.exports = router;

You can find other mistakes in my code,because ive tried many different ways.Here is passport.js config file

const JwtStrategy = require('passport-jwt').Strategy,
ExtractJwt = require('passport-jwt').ExtractJwt;
const config = require("./data");
const mongoose = require("mongoose");
const User = require("../models/specialist");

module.exports = function(passport){
    let cookieExtractor = function(req) {
        var token = null;
        if (req && req.cookies)
        {
            token = req.cookies['Authorization'];
        }
        return token;
    };
    let opts = {}
    opts.jwtFromRequest = cookieExtractor;
    opts.secretOrKey = config.JWT_SECRET;
    passport.use(new JwtStrategy(opts, function(jwt_payload, done) {
        User.findOne({name:jwt_payload._doc.name}, function(err, user) {
            if (err) {
                console.log(err);
                return done(err, false);
            }
            if (user) {
                console.log("OK 200");
                return done(null, user);
            } else {
                console.log("no user");
                return done(null, false);
                // or you could create a new account
            }
        });
    }));
}


//   // Google OAuth Strategy
//   passport.use('googleToken', new GooglePlusTokenStrategy({
//     clientID: config.oauth.google.clientID,
//     clientSecret: config.oauth.google.clientSecret
//   }, async (accessToken, refreshToken, profile, done) => {
//     try {
//       // Should have full user profile over here
//       console.log('profile', profile);
//       console.log('accessToken', accessToken);
//       console.log('refreshToken', refreshToken);

//       const existingUser = await User.findOne({ "google.id": profile.id });
//       if (existingUser) {
//         return done(null, existingUser);
//       }

//       const newUser = new User({
//         method: 'google',
//         google: {
//           id: profile.id,
//           email: profile.emails[0].value
//         }
//       });

//       await newUser.save();
//       done(null, newUser);
//     } catch(error) {
//       done(error, false, error.message);
//     }
//   }));

//   passport.use('facebookToken', new FacebookTokenStrategy({
//     clientID: config.oauth.facebook.clientID,
//     clientSecret: config.oauth.facebook.clientSecret
//   }, async (accessToken, refreshToken, profile, done) => {
//     try {
//       console.log('profile', profile);
//       console.log('accessToken', accessToken);
//       console.log('refreshToken', refreshToken);

//       const existingUser = await User.findOne({ "facebook.id": profile.id });
//       if (existingUser) {
//         return done(null, existingUser);
//       }

//       const newUser = new User({
//         method: 'facebook',
//         facebook: {
//           id: profile.id,
//           email: profile.emails[0].value
//         }
//       });

//       await newUser.save();
//       done(null, newUser);
//     } catch(error) {
//       done(error, false, error.message);
//     }
//   }));

  // LOCAL STRATEGY
//   module.exports = function(passport){
//   passport.use(new LocalStrategy(
//     function(username, password, done) {
//      Spec.findOne({ username: username }, function (err, user) {
//         if (err) { return done(err); }
//         if (!user) { return done(null, false); }
//         if (!user.verifyPassword(password)) { return done(null, false); }
//         return done(null, user);
//       });
//     }
//   ));
// }

And this is ajax request for authentication

$('.logInForm').on('submit', function (e) {
            $.ajax({
                type: 'post',
                url: 'http://localhost:3000/users/spec/authenticate',
                data: $(this).serialize(),
                success:function(data){
                    console.log(data);
                    localStorage.setItem("authToken",data.token);
                }    
            }).done(function(data){
                if(data.token){
                    location.href="http://localhost:3000/users/user";
                }else{
                    console.log("err");
                }
            });
            e.preventDefault();
        });

Thank you very much.

Answer 1

This is due to your code trying to send multiple responses from the authenticate function.

res.json ({ success: true, token: 'bearer ' + token }); // 1st Response
res.redirect("/users/user"); // 2nd Response

Remove one of them which you don't use.