1.while loop:-
A while loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition. The while loop can be thought of as a repeating if statement.
Syntax :
while ( boolean condition);
{
loop statements
}
Flowchart:-
Example:-
<script type =
"text/javaScript"
>
// JavaScript program to illustrate while loop
var
x = 1;
// Exit when x becomes greater than 4
while
(x <= 4)
{
document.write(
"Value of x:"
+ x +
"<br />"
);
// increment the value of x for
// next iteration
x++;
}
< /script>
2. For loop:-
for loop provides a concise way of writing the loop structure. Unlike a while loop, a for statement consumes the initialization, condition and increment/decrement in one line thereby providing a shorter, easy to debug structure of looping.
Syntax:
for (initialization condition; testing condition; increment/decrement)
{
statement(s)
}
Flowchart:-
Example:-
<script type =
"text/javaScript"
>
// JavaScript program to illustrate for loop
var
x;
// for loop begins when x=2
// and runs till x <=4
for
(x = 2; x <= 4; x++)
{
document.write(
"Value of x:"
+ x +
"<br />"
);
}
< /script>
3. do while loop:-
do while loop is similar to while loop with only difference that it checks for condition after executing the statements, and therefore is an example of Exit Control Loop.
Syntax:
do
{
statement
} while (condition);
Flowchart:-
Example:-
<script type =
"text/javaScript"
>
// JavaScript program to illustrate do-while loop
var
x = 21;
do
{
// The line while be printer even
// if the condition is false
document.write(
"Value of x:"
+ x +
"<br />"
);
x++;
}
while
(x < 20);
< /script>