How to write async route handlers — Intermediate

Node / Express Async and await in Express

Mark controller functions async and await service/Knex calls. Always forward failures with next(err) so the error middleware can respond.

Learn: Async handlers must forward rejections with `next(err)`—otherwise Express may not invoke your error middleware. Wrapping async functions or using a small `asyncHandler` utility removes repetitive try/catch blocks.

Supplementary examples

asyncHandler wrapper

function asyncHandler(fn) {
  return (req, res, next) => {
    Promise.resolve(fn(req, res, next)).catch(next);
  };
}

router.get("/", asyncHandler(async (req, res) => {
  const rows = await service.list();
  res.json({ data: rows });
}));

Course example

async function create(req, res, next) {
  try {
    const created = await service.create(req.body);
    res.status(201).json({ data: created });
  } catch (err) {
    next(err);
  }
}

Additional references & examples

MDN: async/await
JavaScript async functions used in route handlers.
Knex.js documentation
Query builder, migrations, seeds, and connection configuration.