In this article, we’ll learn useful information about request objects in Express and their properties.
When the user (client) accesses a route, the user sends the Express application a Request.
The request object, often abbreviated as req, represents the HTTP request property.
We can access any data sent with the body, such as URL parameters, query strings, and HTTP headers.
| Property | Description |
|---|---|
| req.params | An object containing properties mapped to the named route “parameters” |
| req.query | An object containing a property for each query string parameter in the route. |
| req.body | Contains key-value pairs of data submitted in the request body |
| req.protocol | Contains the request protocol string (http or https). |
| req.hostname | Contains the hostname derived from the Host HTTP header. |
| req.path | Contains the path part of the request URL. |
| req.originalUrl | Contains the entire request url. |
| req.subdomains | An array of subdomains in the domain name of the request. |
| req.header | An HTTP header that can be used in an HTTP response. |
| req.cookies | An object containing cookies sent by the request |
| res.ip | Contains the remote IP address of the request. |
There are a few ways for us to receive data from users. For example, we can use req.params, req.query, and req.body.
req.params
// GET https://example.com/user/123
app.get("user/:id", (req, res) => {
console.log(req.params.id); // "123"
});
req.query
// GET https://example.com/user?userID=123&action=submit
app.get("user/", (req, res) => {
console.log(req.query.userID); // "123"
console.log(req.query.action); // "submit"
});
req.body
// POST https://example.com/login {username: "anna", password: "1234"}
app.get("login/", (req, res) => {
console.log(req.body.username); // "anna"
console.log(req.body.password); // "1234"
});
We can access an object that stores URL information such as protocol, hostname, path, and subdomains with a res object to handle URL-related tasks.
// https://learn.devhandbook.com/search?keyword=express
app.get("/search", (req, res) => {
console.log(req.protocol); // "https"
console.log(req.hostname); // "devhandbook.com"
console.log(req.path); // "/search"
console.log(req.originalUrl); // "/keyword=express"
console.log(req.subdomains); // "["learn"]"
});
In addition to sending data and users, the browser also sends headers containing additional information such as content-type, content-length, and other information.
app.post("/login", (req, res) => {
req.header("Content-Type");
req.header("Content-Length");
req.header("user-agent");
req.header("Authorization");
});
When using cookie-parse middleware, the req.cookies object will include the user’s cookies.
If the request contains no cookies, it defaults to {}.
app.post("/login", (req, res) => {
req.cookies.isShowPopup;
req.cookies.sessionID;
});