ActionScript for Flash MX: The Definitive Guide, Second Edition

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

The for Loop

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time through the loop. The do-while statement’s syntax is somewhat like an inverted

while statement:

do {

substatements

} while (condition);

The keyword do begins the loop, followed by the substatements of the body. On the

interpreter’s first pass through the do-while loop,

substatements are executed before

condition is ever checked. At the end of the substatements block, if condition is true,

the loop is begun anew and substatements are executed again. The loop executes

repeatedly until

condition is false, at which point the do-while statement ends. Note

that a semicolon is required following the parentheses that contain the

condition.

Obviously, do-while is handy when we want to perform a task at least once and per-

haps subsequent times. In Example 8-2 we duplicate a series of twinkling-star movie

clips from a clip called

starParent and place them randomly on the Stage. Our gal-

axy will always contain at least one star, even if

numStars is set to 0.

Did you notice that we sneakily updated the variable

i in the test expression?

Remember from Chapter 5 that the post-increment operator both returns the value

of its operand and also adds 1 to that operand. The increment operator is very conve-

nient (and common) when working with loops.

The for Loop

A for loop is essentially