var closeButton = document.getElementById("closeButton");
    var bottomPart = document.getElementById("bottomPart");
    closeButton.onclick = function () {
        animate(bottomPart, {"height": 0}, function () {
            animate(bottomPart.parentNode, {"width": 0});
        });
    }


    function animate(obj, json, fn) {
        clearInterval(obj.timer);
        obj.timer = setInterval(function () {
            //如果本次执行完成后 所有的属性都达到了目标值 就可以清理了
            var flag = true;//假设所有的属性都达到了目标值
            for (var k in json) {
                var leader = parseInt(getStyle(obj, k)) || 0;
                var target = json[k];
                var step = (target - leader) / 10;
                step = step > 0 ? Math.ceil(step) : Math.floor(step);
                leader = leader + step;
                obj.style[k] = leader + "px";
                if (leader != target) {
                    flag = false;//告诉标记我还没达到
                }
            }
            //到了这里还是true就说明 没有任何人告诉falg自己是false
            //也就是说都达到了
            if (flag) {
                clearInterval(obj.timer);
                if (fn) {
                    fn();//有回调函数才调用
                }
            }
        }, 15);
    }