For Loops

Another useful programming structure is the loop. JavaScript provides several ways to repeat commands easily. Let's start with the for loop. The following html was written with JavaScript:

• The for loop requires three parameters:
  The first parameter is the initial setting for the loop variable. In this case we initialize a variable (i) and set i to 1.
• The second parameter is the condition, which must remain true to keep the loop running. In this case, the condition is "as long as i is less than or equal to 10."
• The third parameter is the increment expression which is often used to increment the variable. In this case we add 1 to i at each iteration of the loop.

<script language="Javascript" type="text/javascript">
for (var i=1; i<=10; i=i+1)
{
document.write("<strong>This is loop item " + i + "</strong><br />");
}
</script>

A shortcut method of writing the above is as follows:

<script language="javascript" type="text/javascript">
for (i=1; i<=10; i++)
{
document.write("<strong>This is loop item " + i + "</strong><br />");
}
</script>

The same three parameters are used, but with abbreviated coding. i=1 initializes the starting variable, and i++ adds 1 to the variable each time the loop runs (iteration).