AS3: cast or “as”?

Question

Is there any difference of use, efficiency or background technique between

var mc:MovieClip = MovieClip(getChildByName(\"mc\"));

and

<

Answer 1

Prefer the use of a cast to the use of the as operator. Use the as operator only if the coercion might fail and you want the expression to evaluate to null instead of throwing an exception.

Do this:

IUIComponent(child).document

Not this:

(child as IUIComponent).document

Coding Conventions