Ensuring that variable is initialized only once in a movieclip

Question

Guys, what is the way to ensure that variable is initialized only once in each instance of a movieclip?
I tried:
if (!isLocked)
    trace("setting up isLocked variable");
      var isLocked:Boolean = new Boolean(false);//I need this variable to be initialized only once for each instance of this movieclip and to value of false
but this doesn't work.
Any ideas?

Answer 1

Note that new Boolean() makes zero sense. And this is the beef I have with the convention of checking for existence with !someVariable. Because inexperienced programmers will use that logic with Boolean (which always exists if you're checking it, but is either true or false) or Numbers, which might exist with a value of zero and will make that expression false.
Try
if (!this.hasOwnProperty('isLocked')) {
     var isLocked:Boolean = true;
This may not work because of variable hoisting in AS. It's hard to know what the addFrameScript code will do to this in the background.
Note that you can avoid this by using a proper Class with accessors and mutators and avoiding timeline code.