如何向客户端发送错误消息？

Question

I am using passport with local strategy .but I want to send message and status when credential is not match or ( user is not exit is DB )

here is code

router.js

const passport = require('passport');
const passportConfig = require('../passport')
const passportSignIn = passport.authenticate('local', { session: false });

router.route('/login',)
    .post(passportSignIn,controller.login)

on controller file

 login: async (req, res, next) => {
        console.log(req.body);
        res.json({status:200})

    }

passport.js

passport.use(new LocalStrategy({
    usernameField: 'email'
}, async (email, password, done) => {

    const user = await db.User.findOne({where: {email: email}});
    if (!user) {
        return done(null, false,{message:"No user exit"});
    }
    const isMatch = await bcrypt.compare(password, user.dataValues.password);
    console.log(isMatch, 'isMatch');
    if (!isMatch) {
        return done(null, false);
    }

    // Otherwise, return the user
    done(null, user);

}))

Client code

when user click on login button it goes to /login path first it goes to passportSignIn function or below function.

 `new LocalStrategy({
    usernameField: 'email'
}, async (email, password, done) => {`

now if user not found I want to send this message on the client as the response ("No user exit")

return done(null, false,{message:"No user exit"});

Answer 1

You have to update your login controller, like so:

login: (req, res, next) => {
        console.log(req.body);
        passport.authenticate('yourStrategy', function(err, user, info) {
            if (err) {
              return res.status(500).json("Internal Server Error");
            }
            if (!user) {
              // This 'info' variable below would be - { message: "No user exit" }
              // as you passed in the done() callback as the third param
              return res.status(404).json(info.message);
            }
        }
      }