Setup error handlers in express/mongoose/mongoDB - mongodb

Question

I'm currently part of a web dev Bootcamp and my current project is requesting I create error handlers in a specific manner that I do not understand. Below is a screenshot of the directions . . .
Here are my current files in hopes that it makes sense . . .
/* app.js */
const express = require('express');
const mongoose = require('mongoose');
const userRouter = require('./routes/users');
const cardRouter = require('./routes/cards');
const { PORT = 3000 } = process.env;
const app = express();
mongoose.connect('mongodb://localhost:27017/aroundb', {
useNewUrlParser: true,
useCreateIndex: true,
useFindAndModify: false,
useUnifiedTopology: true,
});
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use((req, res, next) => {
req.user = { _id: '60c4e0e2a80be4c8c2de5474' };
next();
});
app.use('/users', userRouter);
app.use('/cards', cardRouter);
app.listen(PORT, () => logMsg(`listening on port ${PORT} . . .`));
/* routes/users.js */
const express = require('express');
const { getUsers, getUser, createUser } = require('../controllers/users');
const router = express.Router();
router.get('/', getUsers);
router.get('/:id', getUser);
router.post('/', createUser);
module.exports = router;
/* controllers/users.js */
const User = require('../models/user');
module.exports.getUsers = (req, res) => {
User.find({})
.then((users) => res.status(200).send({ data: users }))
.catch((err) => res.status(500).send({ message: err }));
};
module.exports.getUser = (req, res, next) => {
User.findById(req.params.id)
.then((user) => res.send({ data: user }))
.catch((err) => res.status(404).send({ message: err }));
};
module.exports.createUser = (req, res) => {
const { name, about, avatar } = req.body;
User.create({ name, about, avatar })
.then((user) => res.status(201).send({ data: user }))
.catch((err) => res.status(400).send({ message: err }));
};
My questions are:
Where should the code example provided (in the screenshot) go? Am I creating a separate controller or middleware? Or maybe it goes in the already coded controller?
Would I be creating my own errors and using a conditional to read the message?
I already thought I was handling errors, as seen in controllers/users.js, is that not the case?
NOTE: My apologies, I know that since it's from a course it might not make sense outside the context of the lesson(s). I also know there are various ways projects can be coded/solved. Unfortunately, my Bootcamp does not have live instruction, just a slack channel where 97% of responses come from Alumni. Please do not hesitate to ask questions that may help clarify things.

Answer 1

It seems you're directly sending an error in the last two cases, without knowing which type of it is, however it looks fine for fetching all users (1st case).
The workaround that might help you is,
Get user :
User.findById(req.params.id), function(err, user) {
if(err) {
return res.status(500).send({ message: "Default error" });
} else if (!user) {
return res.status(404).send({ message: "User not found" });
}
}
For creating a user you need to manually verify all the fields that are required in schema for ex.,
createUsers : {
const { name, about, avatar } = req.body;
if (name === null || about === null || avatar === null) {
return res.status(400).send({
message : "Required data missing in request"
})
}
... // create user
}