When you listen for connections on a route in Express, the callback function will be invoked on every network call with a Request object instance and a Response object instance.

Example:

app.get('/', (req, res) => res.send('Hello World!'))

Here we used the Response.send() method, which accepts any string.

You can send JSON to the client by using Response.json(), a useful method.

It accepts an object or array, and converts it to JSON before sending it:

res.json({ username: 'Flavio' })

Lessons in this unit:

0:	Introduction
1:	Introduction to Express
2:	Request parameters
3:	Send a response to the client
4:	▶︎ Send a JSON response
5:	Manage cookies
6:	Work with HTTP headers
7:	Handling redirects
8:	Routing
9:	Template engines
10:	Middleware
11:	Serving Static Assets with Express
12:	Send files to the client
13:	Sessions
14:	Validating and sanitizing input
15:	Handling form data
16:	Handling CORS
17:	HTTPS with a self-signed certificate
18:	HTTPS with Let's Encrypt
19:	Handling file uploads
20:	Build a REST API with MongoDB