flash导航菜单代码问题

speedY = spy*(tarY-this._y);
this._y += speedY;
这是一个缓冲效果
MovieClip.prototype.sMove = function(spy, tarY)
的意思就是给flash里的MovieClip类加一个sMove方法
加了方法后你就可以用了
比如下面这个代码:
////////////////
MovieClip.prototype.sMove = function(spy, tarY) {
speedY = spy*(tarY-this._y);
this._y += speedY;
trace("x="+String(this._x)+" y="+String(this._y));
};
_root.createEmptyMovieClip("mc", _root.getNextHighestDepth());
with (mc) {
_x = 200;
_y = 200;
beginFill(0xff0000, 100);
lineTo(0, 0);
lineTo(30, 0);
lineTo(30, 30);
lineTo(0, 30);
endFill();
}
mc.onEnterFrame = function() {
this.sMove(0.1, 0.2);//mc用了sMove的方法
};