We all now that Flex is very much like Java. Do not forget then that in Java the expressions are evaluated from left to right. So, if you have an expression:

a = a && b;


and a is false, b will not be looked at. This is important to remember in case when b is some expression and you want it to be evaluated no matter what a is:

a = a && anImportantUpdateFunction();


If a is false, then anImportantUpdateFunction() will not be called.