JavaScript for Loop

From http://www.w3schools.com (Copyright Refsnes Data)

# JavaScript For Loop

Loops in JavaScript are used to execute the same block of code a specified number of times or while a specified condition is true.

## Examples

For loop
How to write a for loop. Use a For loop to run the same block of code a specified number of times.

Looping through HTML headers
How to use the for loop to loop through the different HTML headers.

## JavaScript Loops

Very 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

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.

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

    <html>
    <body>
    <script type="text/javascript">
    var i=0;
    for (i=0;i<=10;i++)
    {
    document.write("The number is " + i);
    document.write("<br />");
    }
    </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 while loop

The while loop will be explained in the next chapter.

From http://www.w3schools.com (Copyright Refsnes Data)