setInterval在类中如何使用?

Question

var _Ad2 = function(P,D,S){
this.dd = "kkk";
this.imgInterval = setInterval(this.flowImg, 2000);
}
_Ad2.prototype = {
flowImg:function(){alert(this.dd)}
}
如上所示,出现的是undefined,怎么让它能显示出kkk呢?

Answer 1

<script>
    var _Ad2 = function(P,D,S){
        this.dd = "kkk";
        var obj=this;
        this.imgInterval = setInterval(function(){obj.flowImg.call(obj)}, 2000);
    }
    _Ad2.prototype = {
        flowImg:function(){alert(this.dd)}
    }    var a=new _Ad2("p","d","s");
</script>