Sending JSON and Status Codes

Sending JSON and Status Codes

res.json() serialises any JavaScript value to JSON, sets the Content-Type: application/json header, and sends the response. You should chain .status() before it when you need a non-200 code.

app.post("/items", (req, res) => {
  const item = { id: 42, name: "Widget" }; // normally from DB
  res.status(201).json(item);
});

app.get("/items/:id", (req, res) => {
  const found = false; // replace with real lookup
  if (!found) {
    return res.status(404).json({ error: "Item not found" });
  }
  res.json({ id: req.params.id });
});

Common HTTP Status Codes

1. 200 OK — successful GET or PATCH
2. 201 Created — resource successfully created (POST)
3. 204 No Content — successful DELETE with no body
4. 400 Bad Request — client sent invalid data
5. 401 Unauthorized — missing or invalid credentials
6. 403 Forbidden — authenticated but not authorised
7. 404 Not Found — resource does not exist
8. 409 Conflict — e.g. duplicate email on signup
9. 422 Unprocessable Entity — validation failed
10. 500 Internal Server Error — unexpected server fault