09-Routing_with_Router.md

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09 - Routing with Router

Learning goal: Understand how to modularize your routes to make your code cleaner.

In this exercise we will be moving our routes from Exercise 8 into a seperate router.js file in order to de-clutter our index.js file.

index.js

Like in Exercise 8, we want to import Express and Body Parser, but we also want to import our router.js file so we can make use of the routes that will be contained there.

const express = require('express');
const bodyParser = require('body-parser');
const router = require('./router');

Next we want to declare our Express app and our port:

const app = express();
const port = 3000;

We then want to initialize the JSON Body Parser:

app.use(bodyParser.json());

This is the part of index.js that changes from Exercise 8; we want to replace our three route declarations with the following line:

app.use(router);

This tells the Express app to look at the router module to see how to perform request routing.

Finally, we tell our server to listen:

app.listen(port, () => {
	console.log(`Server running on http://localhost:${port}`);
});

router.js

This file is going to contain all of our Express routes. To create a router, we want to first import Express:

const express = require('express');

then create a new instance of Router:

const router = express.Router();

"[An instance of Router ] is an isolated instance of middleware and routes. You can think of it as a 'mini-application,' capable only of performing middleware and routing functions. Every Express application has a built-in app router." --- Express.js Documentation

This means that we can create a specific set of middleware and routes, optimizing a project's modularity. Since router is like a smaller version of app, we can declare routes in the same way. Since we are declaring the same three routes as Exercise 8, I will just show their declaration and not go into detail:

router.get('/', (req, res) => {
	res.send('Hello index!');
});

router.post('/echo', (req, res) => {
	res.send(req.body);
});

router.get('/:name', (req, res) => {
	const casing = req.query.case;

	if(casing === 'lower') {
		res.send(`Hello ${req.params.name.toLowerCase()}!`);
	} else if(casing === 'upper') {
		res.send(`Hello ${req.params.name.toUpperCase()}!`);
	} else {
		res.send(`Hello ${req.params.name}!`);
	}
});

Finally, we want to export our router:

module.exports = router;

Our server will function the same as in Exercise 8, but now we have two smaller and easier to read files!

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