Routing in Express.js

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Arjit Sharma
02 Mins

Routing is the process of defining how your server responds to client requests for specific URLs and HTTP methods. Think of it this way: routing tells your server what to do when someone visits a particular path.

For example - When someone goes to csprimer.in/about, the server should return the About page.

How Routing Works in Express

Express provides methods such as get(), post(), put(), and delete() to handle different HTTP request types. Each method takes:

  • A path (URL pattern)
  • A handler function that processes the request and sends a response

Example: Basic Routes

// Middleware to parse incoming JSON request bodies
// (We’ll explore middlewares in detail later)
app.use(express.json()); 

// Handle GET request to /about
app.get("/about", (req, res) => {
    res.send("This is the About page.");
});

// Handle POST request to /submit
app.post("/submit", (req, res) => {
    const { name, message } = req.body; // Extract data from request body
    if (!name || !message) {
        return res.status(400).send("Missing required fields: name and message.");
    }
    res.send(`Thank you, ${name}! We received your message: "${message}"`);

});

Key Points:

  • app.use(express.json()) enables Express to read JSON data from requests.
  • app.get() handles GET requests (usually for fetching data or pages).
  • app.post() handles POST requests (commonly used for submitting data).
  • req.body contains the data sent by the client.

Common HTTP Methods

MethodPurpose
GETFetch data
POSTCreate data
PUT/PATCHUpdate data
DELETERemove data

Route Chaining

Express also allows you to define multiple handlers for the same route using route chaining. This is useful when you want to group different HTTP methods under a single path

app.route("/users")
   .get((req, res) => res.send("List all users"))
   .post((req, res) => res.send("Create a user"))
   .delete((req, res) => res.send("Delete all users"));

Here:

  • GET /users → Returns a list of users
  • POST /users → Creates a new user
  • DELETE /users → Deletes all users

Conclusion

Routing is the backbone of any Express.js application. By mastering GET, POST, PUT, DELETE, and route chaining, you can build clean, organized APIs that scale easily.

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