TypeError: Cannot read property '_id' of undefined when giving POST request

Question

I have created an entire backend for creating categories for my blog application.

Tech. Used: MongoDB, express-jwt, jwt

Different Files are:

server.js

......

// middlewares
app.use(express.urlencoded({extended: false}));
app.use(express.json());

app.use(morgan('dev'));
app.use(cookieParser());

// cors
if(process.env.NODE_ENV == 'development') {
    app.use(cors({origin: `${process.env.CLIENT_URL}`}));
}

// routes middleware
app.use('/api', authRoutes);
app.use('/api', userRoutes);
app.use('/api', blogRoutes);
app.use('/api', categoryRoutes);
app.use('/api', tagRoutes);

// port
const port = process.env.PORT || 8000;

// Listening App
app.listen(port, () => {
    console.log(`Server is running on PORT ${port}`);
})

caregory.js (Routes)

const express = require('express');
const router = express.Router();
const { create, list, read, remove } = require('../controllers/category')

// Validators
const { runValidation } = require('../validators');
const { categoryCeateValidator } = require('../validators/category');
const { requireSignin, adminMiddleware } = require('../controllers/auth');

router.post('/category', categoryCeateValidator, runValidation, requireSignin, adminMiddleware, create);
router.get('categories', list);
router.get('category/:slug', read);
router.delete('category/:slug', requireSignin, adminMiddleware, remove);


module.exports = router;

category.js (controllers)

const Category = require('../models/category');
const slugify = require('slugify');
const { errorHandler } = require('../helpers/dbErrorHandler');

exports.create = (req, res) => {
    const {name} = req.body;
    let slug = slugify(name).toLowerCase()

    let category = new Category({name, slug});

    category.save((err, data) => {
        if(err) {
            return res.status(400).json({
                error: errorHandler(err)
            })
        }
        res.json(data);
        
    })
}

exports.list = (req, res) => {
    Category.find({}).exec((err, data) => {
        if(err) {
            return res.status(400).json({
                error: errorHandler(err)
            });
        }
        res.json(data);
    });
};

exports.read = (req, res) => {
    const slug = req.params.slug.toLowerCase()

    Category.findOne({slug}).exec((err, category) => {
        if(err) {
            return res.status(400).json({
                error: errorHandler(err)
            });
        }
        res.json(category);
    })
}

exports.remove = (req, res) => {
    const slug = req.params.slug.toLowerCase()

    Category.findOneAndRemove({slug}).exec((err, data) => {
        if(err) {
            return res.status(400).json({
                error: errorHandler(err)
            });
        }
        res.json({
            message: 'Category Deleted Successfully'
        });
    })
}

signin function

exports.signin = (req, res) => {
    const { email, password } = req.body;
    // check if user exist
    User.findOne({ email }).exec((err, user) => {
        if (err || !user) {
            return res.status(400).json({
                error: 'User with that email does not exist. Please signup.'
            });
        }
        // authenticate
        if (!user.authenticate(password)) {
            return res.status(400).json({
                error: 'Email and password do not match.'
            });
        }
        // generate a token and send to client
        const token = jwt.sign({ _id: user._id }, process.env.JWT_SECRET, { expiresIn: '1d' });

        res.cookie('token', token, { expiresIn: '1d' });
        const { _id, username, name, email, role } = user;
        return res.json({
            token,
            user: { _id, username, name, email, role }
        });
    });
};

requireSignin Middleware

exports.requireSignin = expressJwt({
    secret: process.env.JWT_SECRET,
    algorithms: ['HS256'],
    userProperty: "auth" 
});

authMiddleware

exports.authMiddleware = (req, res, next) => {
    const authUserId = req.user._id;
    User.findById({ _id: authUserId }).exec((err, user) => {
        if (err || !user) {
            return res.status(400).json({
                error: 'User not found'
            });
        }
        req.profile = user;
        next();
    });
};

adminMiddleware

exports.adminMiddleware = (req, res, next) => {
    const adminUserId = req.user._id;
    User.findById({ _id: adminUserId }).exec((err, user) => {
        if (err || !user) {
            return res.status(400).json({
                error: 'User not found'
            });
        }

        if (user.role !== 1) {
            return res.status(400).json({
                error: 'Admin resource. Access denied'
            });
        }

        req.profile = user;
        next();
    });
};

Problem: When I POST a request using Postman in order to make a category which is as follows:

Headers and other data I used:

I get the following error:

Solutions I have found online and followed:

1. Initially was using body-parser.json() and changed it to express.json() (latest versions support JSON parsing)
2. Tried both urlencoded extended: true and false.
3. Checked thoroughly my entire code for any mistakes (couldn't find any particular).
4. Checked server.js to ensure that I have defined middleware first then the routes.

Still, this issue persists and I am unable to find a solution.

I am new to backend development and I am unaware of any basic mistakes I may have committed here. I request you to help me find a solution as I am stuck here for days.

I'll be a great help if I can get this sorted out.

Thanks.

Answer 1

I am also facing a different error in requireSignin Middleware, if I am using the secret in back ticks then following error comes:

[enter image description here][1]

export const requireSignin = expressJwt

({
secret: `${process.env.JWT_SECRET}`,
algorithms: ["HS256"], // added later
requestProperty: "user",
});

And if I change my code to this:

export const requireSignin = expressJwt({
secret: process.env.JWT_SECRET,
algorithms: ["HS256"], // added later
requestProperty: "user",
});

Then following error occurs:

[enter image description here][2]

And if I hard code my jwt secret then no error comes, if anyone knows how to rectify it please explain.