护照js检查是否有错误

Question

我正在使用本地护照登录用户：

// route to log in 
    app.post('/login', passport.authenticate('local-login'), function(req, res) { 
        res.send(req.user); 
    }); 

这仅适用于成功的情况，即定义req.user时。如何检查请求中的错误？基本上我想从done（）调用中的护照身份验证代码中提取错误并将其发送回客户端以显示正确的错误消息：

passport.use('local-login', new LocalStrategy({
        username : 'email',
        password : 'password',
        passReqToCallback : true 
    },
    function(req, email, password, done) { 

        console.log('logging in user: ' + email);
        // find a user whose email is the same as the forms email
        // we are checking to see if the user trying to login already exists
        Landlord.findOne({ 'local.email' :  email }, function(err, user) {
            if (err) return done(err);
            if (!user) return done(null, false, { message: 'Incorrect username.' });
            if (!user.validPassword(password)) {
                console.log('wrong pw');
                return done(null, false, { message: 'Incorrect password.' });
            }
            return done(null, user);
        });
    }));