Javascript While Loop

The while loop is an advanced programming mechenism that allows you to do something over and over while a conditional statement is true.
Although the general uses of the while loop are usually a bit complex, this Java Script Academic Tutorial lesson will teach you the basics of how to create a while loop in Java Script.

while Statement

Any while statement executes its statements as long as a specified condition evaluates to true. A while statement looks like as follows:

Syntax

while (variable<=endvalue)
{
code to be executed
}

Example

<html>
<body>
<script type=”text/javascript”>
var i=0;
while (i<=5)
{
document.write(“The number is ” + i);
document.write(“<br />”);
i++;
}
</script>
</body>
</html>

Output

The number is 1
The number is 2
The number is 3
The number is 4
The number is 5

The do…while Loop

The do…while loop is a variant of the while loop. This loop will execute the block of code ONCE, and then it will repeat the loop as long as the specified condition is true.

Syntax

do
{
code to be executed
}
while (variable<=endvalue);

Example

The example below uses a do…while loop. The do…while loop will always be executed at least once, even if the condition is false, because the statements are executed before the condition is tested:

<html>
<body>
<script type=”text/javascript”>
var i=0;
do
{
document.write(“The number is ” + i);
document.write(“<br />”);
i++;
}
while (i<=5);
</script>
</body>
</html>
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