What data can we obtain using an HTTP GET request?

Using an HTTP GET request, we can obtain the following data:

• Query Parameters: Data sent after the ? in the URL, in the format "key=value" and separated by &. Used for filtering, sorting, or transmitting small amounts of data.
• Request Headers: Contain meta-information about the request, such as client type (User-Agent), preferred languages (Accept-Language), accepted content type (Accept), and authentication information (Authorization).
• Request Body: According to the HTTP specification, GET requests should not have a request body. GET is intended only for retrieving information without sending data to the server in the body. Some clients or servers may ignore this, but it is considered incorrect usage of the method.
• URL Path Parameters: Part of the URL that specifies the particular resource the request is directed to. For example, in /users/123, 123 could be a user ID. These parameters are extracted by the server from the request path.

In Node.js, using frameworks like Express.js, access to this data is done as follows:

// Example of obtaining parameters in Express.js
app.get('/users/:userId', (req, res) => {
  const userId = req.params.userId; // Getting the path parameter
  const queryParam = req.query.someParam; // Getting the query parameter
  const userAgent = req.headers['user-agent']; // Getting the request header

  // ... processing data ...
});