no-async-endpoint-handlers.md

Pattern: async Express handler

Issue: -

Description

Express versions before 5.0 do not automatically handle Promise rejections from async handlers. Unhandled rejections will crash the server instead of being passed to the error handler.

Examples

Example of incorrect code:

app.get("/users", async (req, res) => {
  const users = await db.getUsers();
  res.json(users);
});

router.use(async (req, res, next) => {
  req.user = await getUser(req.params.id);
  next();
});

Example of correct code:

app.get("/users", (req, res, next) => {
  db.getUsers()
    .then(users => res.json(users))
    .catch(next);
});

const asyncHandler = fn => (req, res, next) =>
  Promise.resolve(fn(req, res, next)).catch(next);