SWITCH-CASE
Starting with
JavaScript, you can use a switch
statement which handles exactly this situation, and it does so more efficiently
than repeated if...else if statements.
Flow Chart
The following flow chart explains a switch-case statement works.
Syntax
The objective of a switch statement is to give an
expression to evaluate and several different statements to execute based on the
value of the expression. The interpreter checks each case against the value of the expression until a match is found. If
nothing matches, a default condition
will be used.
switch
(expression)
{
case condition 1:
statement(s)
break;
case condition 2:
statement(s)
break;
...
case condition n:
statement(s)
break;
default:
statement(s)
}
The break statements indicate the end of a
particular case. If they were omitted, the interpreter would continue executing
each statement in each of the following cases.
We will explain break
statement in Loop Control chapter.
Example
Try the following example to implement switch-case statement.
<html>
<body>
<script
type="text/javascript">
<!--
var grade='A';
document.write("Entering
switch block<br />");
switch (grade)
{
case 'A':
document.write("Good job<br />");
break;
case 'B': document.write("Pretty good<br />"); break;
case 'C': document.write("Passed<br />"); break;
case 'D': document.write("Not so good<br />"); break;
case 'F': document.write("Failed<br />"); break;
default: document.write("Unknown grade<br
/>")
}
document.write("Exiting
switch block");
//-->
</script>
<p>Set the
variable to different value and then try...</p>
</body>
</html>
Output
Entering switch
block
Good job
Exiting switch
block
Set the variable
to different value and then try...
Break statements play a major role in
switch-case statements. Try the following code that uses switch-case statement
without any break statement.
<html>
<body>
<script
type="text/javascript">
<!--
var grade='A';
document.write("Entering
switch block<br />");
switch (grade)
{
case 'A':
document.write("Good job<br />");
case 'B':
document.write("Pretty good<br />");
case 'C':
document.write("Passed<br />");
case 'D':
document.write("Not so good<br />");
case 'F':
document.write("Failed<br />");
default: document.write("Unknown grade<br
/>")
}
document.write("Exiting
switch block");
//-->
</script>
<p>Set the
variable to different value and then try...</p>
</body>
</html>
Output
Entering switch
block
Good job
Pretty good
Passed
Not so good
Failed
Unknown grade
Exiting switch
block
Set the variable
to different value and then try...
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