Concept:
The if statement specifies a block of code to be executed if a condition
is true:
Syntax:
if (condition) {
block of code to be executed if the condition is true
}
block of code to be executed if the condition is true
}
(1)if example:
<html>
<body>
<script type="text/javascript">
var age = 20;
if( age > 18 ){
document.write("<b>Qualifies for driving</b>");
}
</script>
</body>
</html>
Concept:
The else statement
specifies a block of code to be executed if the condition is false:
Syntax:
if (condition) {
block of code to be executed if the condition is true
} else {
block of code to be executed if the condition is false
}
block of code to be executed if the condition is true
} else {
block of code to be executed if the condition is false
}
(2)if else example:
<html>
<body>
<script type="text/javascript">
var age = 20;
if( age > 18 ){
document.write("<b>Qualifies for driving</b>");
}
else{
document.write("<b>Does not qualify for driving</b>");
}
</script>
</body>
</html>
Concept:
The else if statement
specifies a new condition if the first condition is false:
Syntax:
if (condition1) {
block of code to be executed if condition1 is true
} else if (condition2) {
block of code to be executed if the condition1 is false and condition2 is true
} else {
block of code to be executed if the condition1 is false and condition2 is false
means no codition is matched.block of code to be executed if condition1 is true
} else if (condition2) {
block of code to be executed if the condition1 is false and condition2 is true
} else {
block of code to be executed if the condition1 is false and condition2 is false
}
(3)else if example :
<html>
<body>
<script type="text/javascript">
var book ="history";
if( book == "history" ){
document.write("<b>History Book</b>");
}
else if( book == "maths" ){
document.write("<b>Maths Book</b>");
}
else if( book == "economics" ){
document.write("<b>Economics Book</b>");
}
Else
{
document.write("<b>Unknown Book</b>");
}
</script>
</body>
<html>
Use the switch statement to select one of many blocks of code to be executed.
Concept:
This is how it works:
- The switch expression is evaluated once.
- The value of the expression is compared with the values of each case.
- If there is a match, the associated block of code is executed.
· Break keyword, it breaks out of the switch block.
· This will stop the execution of more code and case testing inside the block.
· When a match is found, and the job is done, it's time for a break. There is no need for more testing.
· The default keyword specifies the code to run if there is no case match
Syntax:
switch(expression)
{
case n1:
code block to be executed if case n1 is matched.
break;
case n2:
code block to be executed if case n2 is matched.
break;
default:
default code block to be execute if no case matched
case n1:
code block to be executed if case n1 is matched.
break;
case n2:
code block to be executed if case n2 is matched.
break;
default:
default code block to be execute if no case matched
break;
}
}
(15)switch example :
<html>
<body>
<script type="text/javascript">
var grade='B';
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 />");
break;
}
</script>
</body>
</html>
========================================================================
JAVASCRIPT EXAMPLE :
<script type="text/javascript">
$a=90;
if($a>=75&&$a<=85)
{
document.write("B grade");
}
else if($a>=85 && $a<=100)
{
document.write("A grade");
}
else if($a>35 && $a<75)
{
document.write("C Grade");
}
else if($a<35)
{
document.write("fail");
}
else
{
document.write("not match");
}
</script>
output:
A grade
JAVASCRIPT EXAMPLE :
<script type="text/javascript">
$a=90;
if($a>=75&&$a<=85)
{
document.write("B grade");
}
else if($a>=85 && $a<=100)
{
document.write("A grade");
}
else if($a>35 && $a<75)
{
document.write("C Grade");
}
else if($a<35)
{
document.write("fail");
}
else
{
document.write("not match");
}
</script>
output:
A grade
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