Tài liệu Why Loops Are Useful pdf

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Why Loops Are Useful

Loops enable Flash to perform an action (or set of actions) repeatedly, which means that

with just a few lines of ActionScript, you can force an action to be executed several

thousand times. In ActionScript, you use loops for tasks that would be difficult or

impossible without loops. For example:

• Creating dynamically generated drop-down lists

• Validating data

• Searching text

• Dynamically duplicating movie clips

• Copying the contents of one array to a new array

• Detecting collisions in games between projectiles and objects

You can use loops to automate any number of tasks, such as dynamically creating movie

clip instances. Suppose your project called for 100 evenly spaced instances of the same

movie clip. You could drag one instance from the library and then create a four- or five￾line looping statement to duplicate the instance 100 times and position each duplicate on

the stage automatically—a great improvement over dragging 100 instances from the

library and aligning each one manually.

Loops are also dynamic. Suppose you scripted a loop to create a menu of 15 choices

(buttons) dynamically. By altering the loop slightly, you could add and remove choices

dynamically. In contrast, adding or removing a button from a manually created menu

involves adding or removing the choice and then moving all of the other choices up or

down one position, and perhaps even rescripting here and there.