Express: handlers (req, res)

Express

Express is the most popular backend framework in Node. It maps a route to a handler function:

app.get("/greeting", (req, res) => {
  res.json({ message: "Hello" });
});

The handler receives two objects:

• req (request): the request. It contains req.params, req.query, req.body, req.headers...
• res (response): the response. It's used to reply:

res.json({ ... });          // responds with JSON (status 200 by default)
res.status(404).json({ ... }); // sets the status code and responds
res.send("text");           // responds with text

In these exercises you write the handler. In the tests we call it with a simulated request and response (crearReq(...) and crearRes()) and check what it responds (res.statusCode, res.body).