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Chapter 2
Understanding Node.js
To understand how Node.js works, first you need to understand a few key features of JavaScript that make it well suited
for server-side development. JavaScript is a simple language, but it is also extremely flexible. This flexibility is the reason
why it has stood the test of time. First-class functions and closures make it an ideal language for web applications.
JavaScript has a bad reputation for being unreliable. However, this notion couldn’t be further from the truth.
Actually, JavaScript’s bad reputation comes from the DOM’s unreliability. The DOM (docment object model) is the
API (application programming interface) that browser vendors provide to interact with the browser using JavaScript.
The DOM has idiosyncrasies between browser vendors. However, JavaScript the language is well-defined and can be
used reliably across browsers and Node.js. In this chapter, we discuss a few fundamentals of JavaScript followed by
how Node.js used JavaScript to provide a highly performant platform for web applications. Other people complain
about how JavaScript handles programming errors (it tries to make invalid code work). However, in such cases, the
developers are really to blame, as they need to be careful when working with a highly dynamic language.
Variables
Variables are defined in JavaScript using the var keyword. For example, the following code segment creates a variable
foo and logs it to the console. (See Listing 2-1.) As you saw in the previous chapter, you would run this code from your
console (terminal on Mac OS X and cmd on Windows) using node variable.js.
Listing 2-1. variable.js
var foo = 123;
console.log(foo); // 123
The JavaScript runtime (the browser or Node.js) has the opportunity to define a few global variables that we
can use in our code. One of them is the console object, which we have been using up to this point. The console
object contains a member function (log), which takes any number of arguments and prints them to the console. We
will discuss more global objects as they are used. As you will see, JavaScript contains most things you expect a good
programming language to have.
Numbers
All numbers in JavaScript have the same floating point number type. Arithmetic operations (+,-,*,/,%) work on
numbers as you would expect, as shown in Listing 2-2.
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