Flash中如何用AS实现帧反播

　　用AS实现帧反向播入
以下是源码：

MovieClip.prototype.backward = function() {
this.gotoAndStop(this._totalframes);
this.onEnterFrame = function() {
this.gotoAndStop(this._currentframe-1);
if (this._currentframe == 1) {
delete this.onEnterFrame;
}
};
};