The School

Is there a way, in AS3, to check whether or not a variable is defined?

Thanks.

If the variable is a number, then you know it hasn't been defined if it's value is NaN.

Code:

var i:Number; if(isNaN(i)) { trace("Our variable i has not been defined"); } else { trace("The value of i is "+i); }

For numbers we use the function isNaN, it returns a Boolean.

For other objects like strings, movieclips, sprites, and I think everything else, it will be null if it's undefined.

Code:

var o:MovieClip; if(o == null) { trace("o is null"); } else { trace(o.x); }