A while loop just looks at a short comparison and repeats until the comparison is no longer True.

1. The while loop

The while loops don't necessarily use a variable to count. Instead, they execute as long as a condition is True. In fact, if the condition starts out as false, the statements won’t execute at all.

The while statement includes the condition in parentheses, and it is followed by a block of statements within braces. Here is its syntax:
while (condition) {
  code to be executed
}
Here's the earlier example, from the "for" instruction, this version use the "while" loop.
<script type="text/javascript"><!--
var i = 0;
while (i<5) {
  document.write("<br /> i = "+i);
  i++;
}
--></script>
- First it's declared a variable "i" with the value of 0. The "while" statement checks the condition (here i<5), which it's True and permits the execution of block code inside the brackets. The "i++" increments the value of "i" and check again the condition. The loop will stop when the "i" reach 5.
- This script displays the following results:
i = 0
i = 1
i = 2
i = 3
i = 4

2. do ... while loops

The do...while loop is a variant of the "while" loop. First will be executed the block of code, and then it will repeat the loop as long as the specified condition is true.

The syntax is:
do {
  code to be executed
}
while (condition)
Here is a simple example:
<script type="text/javascript"><!--
var x = 8;
do {
  document.write("<br /> x = "+x);
  x++;
}
while (x<5)
--></script>
- This example display "x = 8".
As you can notice, although the condition is false (x<5), the code of braces is still executed once.

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which tag is used in <table> to create table header cell?
<thead> <th> <td>
<table><tr>
  <th>Title 1</th>
  <th>Title 2</th>
</tr></table>
Which CSS property sets the distance between lines?
line-height word-spacing margin
.some_class {
  line-height: 150%;
}
Which function opens a new browser window.
alert() confirm() open()
document.getElementById("id_button").onclick = function(){
  window.open("http://coursesweb.net/");
}
Indicate the PHP function that returns an array with names of the files and folders inside a directory.
mkdir() scandir() readdir()
$ar_dir = scandir("dir_name");
var_export($ar_dir);
While loops

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