const
multiline
=
`line1
line2
line3`
;
For this reason, I avoid multiline string syntax: it forces me to either abandon inden‐
tation that makes code easier to read, or include whitespace in my multiline strings
that I may not want. If I do want to break strings up over multiple lines of source
code, I usually use string concatenation:
const
multiline
=
"line1\n"
+
"line2\n"
+
"line3"
;
This allows me to indent my code in an easy-to-read fashion, and get the string I
want. Note that you can mix and match types of strings in string concatenation:
const
multiline
=
'Current temperature:\n'
+
`\t
${
currentTemp
}
\u00b0C\n`
+
"Don't worry...the heat is on!"
;
Numbers as Strings
If you put a number in quotation marks, it’s not a number—it’s a string. That said,
JavaScript will automatically convert strings that contain numbers to numbers as nec‐
essary. When and how this happens can be very confusing, as we will discuss in
. Here’s an example that illustrates when this conversion happens, and when
it doesn’t:
const
result1
=
3
+
'30'
;
// 3 is converted to a string; result is string '330'
const
result2
=
3
*
'30'
;
// '30' is converted to a number; result is numeric 90
As a rule of thumb, when you want to use numbers, use numbers (that is, leave off the
quotes), and when you want to use strings, use strings. The gray area is when you’re
accepting user input, which almost always comes as a string, leaving it up to you to
convert to a number where appropriate. Later in this chapter, we will discuss techni‐
ques for converting among data types.
Booleans
Booleans are value types that have only two possible values:
true
and
false
. Some
languages (like C) use numbers instead of booleans: 0 is
false
and every other num‐
ber is
true
. JavaScript has a similar mechanism, allowing any value (not just num‐
bers) to be considered “truthy” or “falsy,” which we’ll discuss further in
.
Be careful not to use quotation marks when you intend to use a boolean. In particu‐
lar, a lot of people get tripped up by the fact that the string
"false"
is actually truthy!
Here’s the proper way to express boolean literals:
44 | Chapter 3: Literals, Variables, Constants, and Data Types
