ActionScript for Flash MX: The Definitive Guide, Second Edition

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Chapter 8: Loop Statements

clip instances that aren’t transparent to the left edge of the Stage, and we skip the

loop body for transparent instances:

for (var prop in _root) {

if (typeof _root[prop] = = "movieclip") {

if (_root[prop]._alpha < 100) {

continue;

}

_root[prop]._x = 0;

}

}

Maximum Number of Iterations

As noted earlier in this chapter, loops are not allowed to execute forever in Action-

Script. In Flash Player 5 or later, loops are limited to 15 seconds. The number of iter-

ations that can be achieved in that time depends on what’s inside the loop and the

computer’s speed. To be safe, you shouldn’t create loops requiring more than even a

few seconds to execute (which is eons in processing terms!). Most loops should take

only milliseconds to finish. If a loop takes longer to complete (for example, because

it’s processing hundreds of strings while initializing a word-scramble game), it’s

worth rewriting the code using a timeline loop, as described in the next section,

“Timeline and Clip Event Loops.” Timeline loops allow us to update the progress of

a script’s execution on screen and avoid the potential display of the error message

shown in Figure 8-1.

When a loop has run for more than 15 seconds in Flash Player 5 or later, an alert box

warns the user that a script in the ...