Java Reference
In-Depth Information
The best way to think of the
switch
statement is “Switch to the code where the case matches.” The
switch
statement has four important elements:
➤
The test expression
➤
The
case
statements
➤
The
break
statements
➤
The
default
statement
The test expression is given in the parentheses following the
switch
keyword. In the previous
example, you are testing using the variable
myName
. Inside the parentheses, however, you could have
any valid expression.
Next come the
case
statements. The
case
statements do the condition checking. To indicate
which
case
statements belong to your
switch
statement, you must put them inside the curly braces
following the test expression. Each
case
statement specifies a value, for example
"Paul"
. The
case
statement then acts like
if (myName == "Paul")
. If the variable
myName
did contain the value
"Paul"
, execution would commence from the code starting below the
case "Paul"
statement and
would continue to the end of the
switch
statement. This example has only two
case
statements, but
you can have as many as you like.
In most cases, you want only the block of code directly underneath the relevant
case
statement to execute, not
all
the code below the relevant
case
statement, including any other
case
statements. To achieve this, you put a
break
statement at the end of the code that
you want executed. This tells JavaScript to stop executing at that point and leave the
switch
statement.
Finally, you have the
default
case, which (as the name suggests) is the code that will execute when
none of the other
case
statements match. The
default
statement is optional; if you have no default
code that you want to execute, you can leave it out, but remember that in this case no code will
execute if no
case
statements match. It is a good idea to include a
default
case, unless you are
absolutely sure that you have all your options covered.
Using the switch Statement
trY it out
Let's take a look at the
switch
statement in action. The following example illustrates a simple guessing
game. Type the code and save it as
ch3 _ example3.html
.
<!DOCTYPE html>
<html lang="en">
<head>
<title>Chapter 3, Example 3</title>
</head>
<body>
<script>
var secretNumber = prompt("Pick a number between 1 and 5:", "");
secretNumber = parseInt(secretNumber, 10);
switch (secretNumber) {
