LEARNING JAVASCRIPT - Trang 64

2

Also called a grave accent mark.

const

nan

=

Number

.

NaN

;

// the same as NaN

const

inf

=

Number

.

POSITIVE_INFINITY

;

// the same as Infinity

We’ll discuss the importance of these values in

Chapter 16

.

Strings

A string is simply text data (the word string comes from “string of characters”—a

word originally used in the late 1800s by typesetters, and then later by mathemati‐

cians, to represent a sequence of symbols in a definite order).
Strings in JavaScript represent Unicode text. Unicode is a computing industry stan‐

dard for representing text data, and includes code points for every character or symbol

in most known human languages (including “languages” that might surprise you,

such as Emoji). While Unicode itself is capable of representing text in any language,

that does not mean that the software rendering the Unicode will be capable of render‐

ing every code point correctly. In this book, we’ll stick to fairly common Unicode

characters that are most likely available in your browser and console. If you are work‐

ing with exotic characters or languages, you’ll want to do additional research on Uni‐

code to understand how code points are rendered.
In JavaScript, string literals are represented with single quotes, double quotes, or

backticks.

2

The backtick was introduced in ES6 to enable template strings, which we

will cover shortly.

Escaping

When you’re trying to represent text data in a program that’s made up of text data,

the problem is always distinguishing text data from the program itself. Setting off

strings within quotes is a start, but what if you want to use quotes in a string? To solve

this problem, there needs to be a method of escaping characters so they are not taken

as string termination. Consider the following examples (which do not require escap‐

ing):

const

dialog

=

'Sam looked up, and said "hello, old friend!", as Max walked in.'

;

const

imperative

=

"Don't do that!"

;

In

dialog

, we can use double quotes without fear because our string is set off with

single quotes. Likewise, in

imperative

, we can use an apostrophe because the string

is set off with double quotes. But what if we needed to use both? Consider:

// this will produce an error
const dialog = "Sam looked up and said "don't do that!" to Max.";

40 | Chapter 3: Literals, Variables, Constants, and Data Types