ExternalInterface.call();

Flash Action Script -

var _str:String = "클릭 하였어요~"

var _spr:Sprite = new Sprite();
_spr.graphics.beginFill(0xff0000, 1);
_spr.graphics.drawCircle(0, 0, 10);
this.addChild(_spr);

_spr.buttonMode = true;

_spr.addEventListener(MouseEvent.CLICK, clickHandler);

function clickHandler (e:MouseEvent):void{
    ExternalInterface.call(jsFunc, _str)
}


HTML -

<script>
function jsFunc(str){
    alert(str)
}
</script>