Express.js router.METHOD() Function

The router.METHOD() method provides the routing functionality in Express, where METHOD is one of the HTTP methods, such as GET, PUT, POST, and so on, in lowercase.

Syntax:

router.METHOD(path, [callback, ...] callback)

Parameter: The path parameter specifies the path on the URL and callback is the function which is executed when this path is called.

Return Value: Since, it provides the routing functionality, so it can return responses.

Installation of express module:

1. You can visit the link to Install express module. You can install this package by using this command.

   npm install express

2. After installing the express module, you can check your express version in command prompt using the command.

   npm version express

3. After that, you can just create a folder and add a file for example, index.js. To run this file you need to run the following command.

   node index.js

Example 1: Filename: index.js

var express = require('express');
var app = express();
var router = express.Router();
var PORT = 3000;

// Single route
router.get('/user', function (req, res, next) {
    console.log("GET request called");
    res.end();
});

app.use(router);

app.listen(PORT, function(err){
    if (err) console.log(err);
    console.log("Server listening on PORT", PORT);
});

Steps to run the program:

1. The project structure will look like this:
   
2. Make sure you have installed express module using the following command:

   npm install express

3. Run index.js file using below command:

   node index.js

   Output:

   Server listening on PORT 3000
   

4. Now make GET request to http://localhost:3000/, you can see the following output on your screen:

   Server listening on PORT 3000
   GET request called
   

Example 2: Filename: index.js

var express = require('express');
var app = express();
var router = express.Router();
var PORT = 3000;

// Multiple routes
router.get('/user', function (req, res, next) {
    console.log("GET request called");
    res.end();
});

router.post('/user', function (req, res, next) {
    console.log("POST request called");
    res.end();
});

router.delete('/user', function (req, res, next) {
    console.log("DELETE request called");
    res.end();
})

app.use(router);

app.listen(PORT, function(err){
    if (err) console.log(err);
    console.log("Server listening on PORT", PORT);
});

Run index.js file using below command:

node index.js

Now make GET, POST, DELETE request to http://localhost:3000/, you can see the following output on your screen:

Server listening on PORT 3000
GET request called
POST request called
DELETE request called

Reference: https://expressjs.com/en/4x/api.html#router.METHOD