"while" Loop Statement Example

JavaScript Tutorials - Herong's Tutorial Examples

∟"while" Loop Statement Example

This section provides a JavaScript tutorial example showing how to write a 'while' loop statement.

To help you understand how "while" loop statements work, I wrote the following the JavaScript tutorial example, For_Loop_Statements.html:

<html>
<!-- While_Loop_Statements.html
   Copyright (c) 2002 HerongYang.com. All Rights Reserved.
-->
<head><title>While Loop Statements</title></head>
<body>
<pre>
<script type="text/javascript">
   var i, j, is_prime;
   i = 3;
   while ( i<=30 ) {
      is_prime = true;
      j = 2;
      while ( j<=i/2 ) {
         is_prime = i%j > 0;
         if (!is_prime) break;
         j++;
      }
      if (is_prime)
         document.write("Found a prime number: " + i + ".\n");
      i += 2;
   }
</script>
</pre>
</body>
</html>

This JavaScript uses a nested "while" loop statements to calculate prime numbers. It has the same execution logic as the While_Loop_Statements.html JavaScript.

The output of this sample JavaScript is:

Found a prime number: 3.
Found a prime number: 5.
Found a prime number: 7.
Found a prime number: 11.
Found a prime number: 13.
Found a prime number: 17.
Found a prime number: 19.
Found a prime number: 23.
Found a prime number: 29.