ValidationError not caught by express error handler - node.js

Question

In my mongoose schema, I have a field type that is required. I am using a custom error handler in express defined as
const notFound = (req, res, next) => {
const error = new Error(`Not found-${req.originalUrl}`);
res.status(404);
next(error);
};
const errorHandler = (err, req, res, next) => {
const statusCode = res.statusCode === 200 ? 500 : res.statusCode;
res.status(statusCode);
res.json({
message: err.message,
stack: process.env.NODE_ENV === 'production' ? null : err.stack,
});
};
and use the error handlers at the bottom of my server.js file as
app.use(notFound);
app.use(errorHandler);
However, when I try to test the route that posts an entry using Postman, the request will be stuck and no response is sent back, and in the terminal there is an error saying that UnhandledPromiseRejectionWarning: ValidationError: ...
My question is: shouldn't my custom error handler catch the error?

Answer 1

Make sure that you're forwarding the error wherever you're performing your mongoose action. There you should be able to forward that to your middleware.
For example you can try something like this:
example.findById(req.id, async function(err, foundRecord){
if(err) {
next(err);
} else {
....
}
});
Let me know if that works.

Answer 2

You can try with this simple HttpError:
Create HttpError.js:
class HttpError extends Error {
constructor(statusCode, message = 'Internal Server Error') {
super(message);
this.statusCode = statusCode;
this.isSuccess = false;
this.isError = true;
this.errorMessage = message;
this.data = null;
}
}
module.exports.HttpError = HttpError;
You can create for an example: NotFoundError extends HttpError :
const { HttpError } = require('../HttpError');
class NotFoundError extends HttpError {
constructor(message = 'Not Found') {
super(404, message);
}
}
module.exports.NotFoundError = NotFoundError;
Now, in your app.js, you can handle error like this code below:
// handle notFoundError
app.use((req, res, next) => { throw new NotFoundError() });
// handle unexpectedly error or another error
app.use((error, req, res, next) => {
res.status(error.statusCode || 500).send(error);
})
If you want to look at the tutorial, for mys, but use the indonesian language ("But you don't have to listen, just look at the concept"), you can check it out here:
Handle Express Error: https://www.youtube.com/watch?v=GwS6KJmO9w8&list=PLREvIK3N7Ga6F669gbDCDMwrn37Uq32-O&index=13
Handle HttpError: https://www.youtube.com/watch?v=VoorNGvDypE&list=PLREvIK3N7Ga6F669gbDCDMwrn37Uq32-O&index=14
Or for example code, you can check it out on this github repo: https://github.com/12bedeveloper/basic-express
Keep learn.