Looping:
Looping is used when some block of code will be
exected a number of times, knowing in advance how
many times the script will be run; or while a
specified condition is true. We use the loops "for",
"while", and "Do while".
1. Loop for
FOR
Example:
<body>
<script type="text/javascript">
for (i = 1; i <= 4; i++)
{
document.write(" The number is : " + i + "<br />");
}
</script>
</body>
The output is:
The number is : 1
The number is : 2
The number is : 3
The number is : 4
2. While:
<body>
<script type="text/javascript">
i=3;
while (i<=7)
{
document.write(" The number is : " + i + "<br />");
i=i+1;
}
</script>
</body>
The variable "i" is equal to 3. While "i" is less than, or equal to,
7, the loop will continue to run; "i" is increased by 1 each time
the loop runs.
The output is:
The number is : 3
The number is : 4
The number is : 5
The number is : 6
The number is : 7
3. Do while:
<body>
<script type="text/javascript">
var i = 3;
do
{
document.write(" The number is : " + i + "<br />");
i++;
}
while (i<1);
</script>
</body>
The do...while loop will execute the block of code
once. If the condition in while (condition) statement
is true, the loop will continue, otherwise, it stops leaving
behind the test first result even if the condition is false.
The output is:
The number is : 3
4. break and continue statement:
Inside a loop, we use the break statement
to stop the loop, and continue statement
to break the current loop and continue with
the next value.
Example
<body>
<script type="text/javascript">
var j=3;
for (j=3;j<=7;j++)
{
if (j==5)
{
break;
}
document.write("<br />The double is :" + j*2 + "<br />");
}
var i=3;
for (i=3;i<=7;i++)
{
if (i==5)
{
continue;
}
document.write("<br />The double of " + i + " is :" + i*2 + "<br />");
}
</script>
</body>
The outputs are:
The double is :6
The double is :8
and:
The double of 3 is :6
The double of 4 is :8
The double of 6 is :12
The double of 7 is :14
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