Actionscript Cookbook

1.5. Repeating an Operation Many Times

Problem

You want to perform a task multiple times within a single frame.

Solution

Use a loop to perform the same task multiple times within a single frame. For example, you can use a for statement:

for (var i = 0; i < 10; i++) {
  // Display the value of i.
  trace(i);
}

Discussion

When you want to execute the same action (or slight variations thereof) multiple times within a single frame, use a looping statement to make your code more succinct, easier to read, and easier to update. You can use a while statement or a for statement for this purpose, but generally a for statement is the better choice. Both statements achieve the same result, but the for statement is more compact and more familiar to most programmers.

The syntax of a for statement consists of five basic parts:

The for keyword

Every for statement must begin with a for keyword.

Initialization expression

The loop typically employs an index variable (a.k.a. a loop counter) that is initialized when the statement is first encountered. The initialization is performed only once regardless of how many times the loop is repeated.

Test expression

A loop should include a test expression that returns true or false. The test expression is evaluated once each time through the loop. Generally, the test expression compares the index variable to another value, such as a maximum number of loop iterations. The overall expression must evaluate to true for the for statement’s body to execute (contrast this ...