How can I create custom error classes in Express?

How can I create custom error classes in Express?

You can create custom error classes by extending the built-in Error class in JavaScript. Here's a simple example:

Can you show me a code example?

Sure! Here's a basic implementation:

class CustomError extends Error {
    constructor(message, statusCode) {
        super(message);
        this.statusCode = statusCode;
        Error.captureStackTrace(this, this.constructor);
    }
}

module.exports = CustomError;

How do I use this custom error class in my Express app?

You can use it in your middleware like this:

app.use((err, req, res, next) => {
    if (err instanceof CustomError) {
        return res.status(err.statusCode).json({ message: err.message });
    }
    res.status(500).json({ message: 'Internal Server Error' });
});