Routing
- Node.js course
- Intermediate
- Lesson 15/116
- 5 min
Learn simple URL routing logic.
Routing
Routing means giving different responses based on the request path (req.url). The simplest way is checking the path with if conditions.
Example: if (req.url === "/") { res.end("Home"); } else if (req.url === "/about") { res.end("About"); } else { res.end("Unknown"); }. Here req.url gives the request path; each path produces a different response. The else branch provides a fallback for unknown paths. This is a simplified version of what frameworks like Express do behind the scenes; frameworks match the path with a more organized table.
Unknown paths
In routing it is good practice to always keep an else branch. This branch gives a fallback response for unmatched paths; this way no request hangs.
Example: if (req.url === "/") { res.end("Home"); } else { res.end("Unknown path"); }. A request to /about gets Unknown path. Usually unknown paths also set a 404 status: res.statusCode = 404; then res.end("Not found"). This clearly tells the user the path is invalid. statusCode is the response's HTTP status code; 200 means success, 404 means not found.
Practice Write two-path routing
Import the http module. Create a server with createServer. Inside the handler check req.url: if "/" call res.end("Home"), otherwise res.end("Unknown"). The ready-made code below starts the server and sends a request to "/".
Starter code
// Import the http module and create a server
// write here
server.listen(3000, () => {
http.get("http://localhost:3000/", (res) => {
let body = "";
res.on("data", (c) => body += c);
res.on("end", () => { console.log("Reply: " + body); server.close(); });
});
});Sample solution
const http = require("http");
const server = http.createServer((req, res) => {
if (req.url === "/") { res.end("Home"); }
else { res.end("Unknown"); }
});
server.listen(3000, () => {
http.get("http://localhost:3000/", (res) => {
let body = "";
res.on("data", (c) => body += c);
res.on("end", () => { console.log("Reply: " + body); server.close(); });
});
});Expected output
Yanıt: Ana sayfa
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which property is basic routing based on?
if (req.url === "/x") { ... }- req.method
- res.end
- req.url Correct answer
- server.listen
Explanation: req.url gives the request path; routing uses it.
2 Match each path to its response
| Term | Meaning |
|---|---|
"/" |
Home |
"/about" |
About |
else |
Unknown |
req.url |
Request path |
3 Complete the routing condition
if (req.____ === "/") { res.end("Ana sayfa"); }if (req.url === "/") { res.end("Ana sayfa"); }Explanation: req.url holds the request path.