The while loop is an advanced programming technique 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 lesson will teach you the basics of how to create a while loop in Javascript. Javascript While Loop Explained There are two key parts to a Javascript while loop: The conditional statement which must be True for the while loop's code to be executed. The while loop's code that is contained in curly braces "{ and }" will be executed if the condition is True.
When a while loop begins the Javascript interpreter checks the condition statement is true. If it is the code between the curly braces is executed. At the end of the code segment "}" the while loop loops back to the condition statement and begins again. If the condition statement is always True then you will never exit the while loop, so be very careful when using while loops! The while loopThe while loop is used when you want the loop to execute and continue executing while the specified condition is true. while (var<=endvalue)
{
code to be executed
} Note: The <= could be any comparing statement. Example Explanation: The example below defines a loop that starts with i=0. The loop will continue to run as long as i is less than, or equal to 10. i will increase by 1 each time the loop runs. <html><body>
<script type="text/javascript">
var i=0;
while (i<=10)
{
document.write("The number is " + i);
document.write("<br />");
i=i+1;
}
</script>
</body></html> Result The number is 0
The number is 1
The number is 2
The number is 3
The number is 4
The number is 5
The number is 6
The number is 7
The number is 8
The number is 9
The number is 10 The do...while Loop The do...while loop is a variation of the while loop. This loop will always execute a block of code ONCE, and then it will repeat the loop as long as the specified condition is true. This loop will always be executed at least once, even if the condition is false, because the code is executed before the condition is tested. do
{
code to be executed
}
while (var<=endvalue); Example <html><body>
<script type="text/javascript">
var i=0;
do{
document.write("The number is " + i);
document.write("<br />");
i=i+1;
}
while (i<0);
</script>
</body></html> Result The number is 0
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