Thursday, May 21, 2009

JavaScript For Loop.


Loops execute a block of code a specified number of times, or while a specified condition is true.

JavaScript For Loop


Often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal lines in a script we can use loops to perform a task like this.

In JavaScript, there are two different kind of loops:

  • for - loops through a block of code a specified number of times.
  • while - loops through a block of code while a specified condition is true.

    The for Loop


    The for loop is used when you know in advance how many times the script should run.

    Syntax.


    for (var=startvalue;var<=endvalue;var=var+increment)
    {
    code to be executed
    }

    Example.


    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 5. i will increase by 1 each time the loop runs.

    Note: The increment parameter could also be negative, and the <= could be any comparing statement.

    Example.


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