In this chapter, we’ll learn the important details of the request and
response objects—which are very much the beginning and end of everything
that happens in an Express application. When you’re building a web server with Express, most of what you’ll be
doing starts with a request object and ends with a response
object.
These two objects originate in Node and are
extended by Express. Before we delve into what these objects offer us,
let’s establish a little background on how a client (a browser, usually)
requests a page from a server and how that page is returned.
The Parts of a URL
We see URLs all the time, but we don’t often stop to think about their component parts. Let’s consider three URLs and examine their component parts:
Protocol
The protocol determines how the request will be
transmitted. We will be dealing exclusively with
http and https. Other common protocols include file and ftp.
Host
The host identifies the server. Servers on your computer (localhost) or a local
network may be identified simply be one word or by a numeric IP
address. On the internet, the host will
end in a top-level domain (TLD) like .com or .net. Additionally, there
may be subdomains, which prefix the hostname. www is a common
subdomain, though it can be anything. Subdomains are
optional.
Port
Each server has a collection of numbered ports. ...
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