Node.js Backend Development Bootcamp · Lesson

Handling Request Data: Body, Query & Params

Route params: req.params
Query string: req.query
Request body: req.body
Headers: req.headers

Master how Express receives and parses incoming data from clients, including route parameters, query strings, JSON bodies, and form submissions.

Where Client Data Comes From

An HTTP request can carry data in several places. An Express handler reads each from a different property of the req object:

app.get('/info', (req, res) => {
  res.json({ params: req.params, query: req.query });
});

Route parameters are named URL segments prefixed with a colon. For /users/:id, a request to /users/42 gives req.params.id === '42'.

They are always strings, so convert to numbers when needed.

app.get('/users/:id', (req, res) => {
  const id = Number(req.params.id);
  res.send('Looking up user ' + id);
});