CHAPTER 3
Literals, Variables, Constants,
and Data Types
This chapter is about data, and how we translate data into a format that JavaScript
can understand.
You’re probably aware that all data is ultimately represented inside a computer as long
sequences of ones and zeros—but for most day-to-day tasks, we want to think about
data in a way that’s more natural to us: numbers, text, dates, and so on. We will call
these abstractions data types.
Before we dive into the data types available in JavaScript, we will discuss variables,
constants, and literals, which are the mechanisms available to us in JavaScript for
holding data.
The importance of vocabulary is often overlooked when you’re
learning to program. While it may not seem important to under‐
stand how a literal differs from a value, or a statement from an
expression, not knowing these terms will hamper your ability to
learn. Most of these terms are not specific to JavaScript, but are
commonly understood in computer science. Having a good grasp
of the concepts is important, of course, but paying attention to
vocabulary makes it easy for you to transfer your knowledge to
other languages, and learn from more sources.
Variables and Constants
A variable is essentially a named value, and as the name implies, the value can change
at any time. For example, if we’re working on a climate control system, we might have
a variable called
currentTempC
:
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