express_error_handling_middleware_typescript_quickstart.ts

1import express, { Request, Response, NextFunction } from 'express';
2
3const app = express();
4const port = 3000;
5
6// Regular route that throws an error
7app.get('/', (req: Request, res: Response) => {
8  throw new Error('BROKEN'); // Express will catch this on its own in synchronous code
9});
10
11// Error-handling middleware functions are defined in the same way as other middleware functions,
12// except error-handling functions have four arguments instead of three: (err, req, res, next).
13app.use((err: any, req: Request, res: Response, next: NextFunction) => {
14  console.error(err.stack);
15  res.status(500).send('Something broke!');
16});
17
18app.listen(port, () => {
19  console.log(`Example app listening on port ${port}`);
20});