switch Statements
Where
if...else
statements allow you to take one of two paths,
switch
statements
allow you to take multiple paths based on a single condition. It follows, then, that the
condition must be something more varied than a truthy/falsy value: for a
switch
statement, the condition is an expression that evaluates to a value. The syntax of a
switch
statement is:
switch
(
expression
) {
case
value1
:
// executed when the result of expression matches value1
[
break
;]
case
value2
:
// executed when the result of expression matches value2
[
break
;]
...
case
valueN
:
// executed when the result of expression matches valueN
[
break
;]
default
:
// executed when none of the values match the value of expression
[
break
;]
}
JavaScript will evaluate
expression
, pick the first
case
that matches, and then exe‐
cute statements until it sees a
break
,
return
,
continue
,
throw
or the end of the
switch
statement (we will learn about
return
,
continue
, and
throw
later). If that
sounds complex to you, you’re not alone: because of the nuances of the
switch
state‐
ment, it’s received a lot of criticism as being a common source of programmer error.
Often, beginning programmers are discouraged from using it at all. I feel that the
switch
statement is very useful in the right situation: it’s a good tool to have in your
toolbox, but like any tool, you should exercise caution, and use it when appropriate.
We’ll start with a very straightforward example of a
switch
statement. If our fictional
sailor has multiple numbers he’s superstitious about, we can use a
switch
statement
to handle them accordingly:
switch
(
totalBet
) {
case
7
:
totalBet
=
funds
;
break
;
case
11
:
totalBet
=
0
;
break
;
case
13
:
totalBet
=
0
;
break
;
case
21
:
totalBet
=
21
;
72 | Chapter 4: Control Flow
