| 3. 5. 1. Using the switch Structure |
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JavaScript offers the switch statement as an alternative to using the if...else structure. |
The switch statement is useful when testing all the possible results of an expression. |
The format of a switch structure looks like the following: |
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switch (expression)
{
case label1:
statement1;
break;
case label2:
statement2;
break;
default:
statement3;
}
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The switch statement evaluates an expression placed between parentheses. |
The result is compared to labels associated with case structures that follow the switch statement. |
If the result is equal to a label, the statement(s) in the corresponding case structure are executed. |
A default is used at the end of a switch structure to catch results that do not match any of the case labels. |
A colon always follows a label. |
Curly brackets {} are used to hold all the case structures together, but they are not used within a case structure. |
The keyword break is used to break out of the entire switch statement once a match is found, thus preventing the default structure from being executed accidentally. |
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<html>
<SCRIPT LANGUAGE='JavaScript'>
<!--
var color = "green";
switch (color)
{
case "red":
document.write("The car is red.");
break;
case "blue":
document.write("The car is blue.");
break;
case "green":
document.write("The car is green.");
break;
default:
document.write("The car is purple.");
}
//-->
</SCRIPT>
</html>
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