Example code

Custom Error class.

• Default to 500 error code.

// HttpError.ts
export default class HttpError extends Error {
  constructor(public message: string, public statusCode: number = 500) {
    super(message);
  }
}

Custom error handler

• Define it as a last middleware, after other app.use() and routes calls.

// app.ts
import HttpError from './HttpError';
// .... other stuff
app.get('/error', () => {
  throw new HttpError('Invalid input', 422);
});
app.use((err, req, res, next) => {
  const { statusCode, message, stack } = err;
  const jsonBody = { status: 'error', statusCode, message };
  res.status(statusCode).json(
    process.env['NODE_ENV'] === 'production'
      ? jsonBody
      : { ...jsonBody, stack } // Show stacktrace if not production
  );
});

Known issues

• Starting with Express 5, route handlers and middleware that return a Promise will call next(value) automatically when they reject or throw an error.
• You can install Express 5 with yarn add express@next.

Useful links

• Error Handling from Express document
• Central Error Handling in Express
• Default error message in Express