when is a good time to use a loop? - actionscript-3

Question

I have been trying to learn actionscript 3 for a while now and there are somethings that get me. Like when should I use a loop(for, while, etc)? I watch videos and read articles on the subject and I always run into this example witch really doesn't help me that much:
for(var i:Number = 0; i < 10; i++)
{
trace(i);
}
If anyone can help me on the subject and maybe let me pick there brain a little I would really appreciate it.
Thank you.

Answer 1

You use loops anytime you need to do repetitive tasks.
So if you had 1000 objects that you needed to perform the same operation on, it will be more practical to use a loop instead of writing variations of the same code 1000 times.
A flash example: Let's say you had 10 movieClips that you wanted to all play on a given action.
you could do this:
mc1.play();
mc2.play();
mc3.play();
mc4.play();
mc5.play();
mc6.play();
mc7.play();
mc8.play();
mc9.play();
mc10.play();
For 10 it's just annoying but not a huge deal. If you had 100, or 1000, or 10000 it would be insane. Plus then what if you need to change your code later?
A better way would be to use a loop. Lets say those 10 clips (or any number of clips) were all the children of a parent object called clips.
for(var i:int=0; i<clips.numChildren;i++){
var mc:MovieClip = clips.getChildAt(i);
mc.play();
}
That code would do the exact same thing. You're looping through all the children of the clips parent, and telling everyone to play. Need to change it to gotoAndPlay(3)? then you just have one line to update.
This is a very simple example (and just one of many reasons you'd use a loop), you can probably guess when you get into working with more complex data and objects how loops help you code repetitive tasks.

Answer 2

In general, I use a for loop when I need an index.
For example I might want an array of indexes that represents which MovieClips in a given array are visible :
var visibleClips:Array = new Array;
for (var index:int = 0;index < arrayOfClips.length;index++)
{
var clip:MovieClip = arrayOfClips[index];
if (clip.visible)
{
visibleClips.push(index);
}
}
A while loop I commonly use for something like removing all the children from a DisplayObject like this :
while (container.numChildren > 0)
{
container.removeChildAt(0);
}
As you can see, I really did not need an index in that situation, so it's simpler to use the while loop.

Answer 3

As my old programming teacher said:
"Use for loops when you know how many iterations you want/need to do"
I.e looping through a list, array, vector etc.
"And use while loops when you are not sure."
I.e looping through a whole file (for reading binary data) or doing continuous events that stops for a certain condition.
That being said you could probably apply both for and while loops for most cases. Personally I mostly use for-loops.
Like prototypical said the while loops is great when removing all children of a container but this could also be achieved using a for loop like:
for(var i:int = 0; i < numChildren; i++)
{
removeChildAt(i); i--;
}