One major change from AS2 was the removal of Numbers being nullable, this was useful for determining if something had been given a value or not, and setting it to a default. One workaround is using NaN, which can be used on the function initializer:
function testNum(num:Number = NaN) { if (isNaN(num)) { trace(num + " no num"); } else { trace("has num: " + num); } } /////////// BEGIN TEST ///////////// var numA:Number; //NaN testNum(); // NaN no num testNum(numA); //NaN no num numA = -1; testNum(numA); //has num: -1 numA = 0; testNum(numA); //has num: 0 numA = 1; testNum(numA); //has num: 1
