ActionScript for Flash MX: The Definitive Guide, Second Edition

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

Further ActionScript Concepts

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17

On line 1, we set the value of the variable x to 1. Then at line 2, we display that value

in the Output window. On line 3, we say, “Take the current value of

x, add 1 to it,

and stick the result back into our variable

x,” so x becomes 2. Then we display the

value of

x in the Output window again. We repeat this process three more times. By

the time we’re done, we’ve displayed a sequence of five numbers in the Output win-

dow. The beauty is that if we now want to change the starting number of our

sequence to 501, we just change the initial value of

x from 1 to 501. Because the rest

of our code is based on

x, the entire sequence changes when we change the initial

value.

That’s an improvement over our first approach, and it works pretty well when we’re

displaying only five numbers, but it becomes impractical if we want to count to

1,000. To perform highly repetitive tasks, we use a loop—a statement that causes a

block of code (i.e., one or more instructions) to be performed a specified number of

times. There are several types of loops, each with its own syntax. One of the most

common loop types is the while loop. Here’s what our counting example would look

like as a while loop instead of as a series of individual statements:

var x = 1;

while (x <= 5) {

trace (x); ...