TweenJS / callback

this.ball.alpha = 0;

function showBall(ziel) {
	ziel.x = Math.random() * 500 + 20;
	ziel.y = Math.random() * 300 + 50;
	ziel.alpha = 0;
	createjs.Tween.get(ziel).to({alpha: 1}, 1000).call(showBall, [ziel]);
}
showBall(this.ball);