带回调函数的js运动框架

function startMove(obj, json, endFun) {
    //开始前关闭之前obj上的定时器
    clearInterval(obj.timer); 

    //定时器
    obj.timer = setInterval(function() {

        var bStop = true; //假设所有值都到目标
        for(var attr in json) {//循环json数组

            //单独处理透明度
            if(attr == 'opacity') {
                var cur = Math.round(parseFloat(getStyle(obj, attr)) * 100);
            } else {
                var cur = parseInt(getStyle(obj, attr));
            }
            //速度处理
            var speed = (json[attr] - cur) / 6;
            speed = speed > 0 ? Math.ceil(speed) : Math.floor(speed);

            //如果当前的没到目标值
            if(cur != json[attr]) 
                bStop = false;

            //运动
            if(attr == 'opacity') {
                obj.style.opacity = (cur + speed) / 100;
                obj.style.filter = 'alpha(opacity:' + (cur + speed) + ')';
            } else {
                obj.style[attr] = cur + speed + 'px';
            }
        }
        //所有的都到达目标值
        if(bStop) {
            clearInterval(obj.timer);
            if(endFun) endFun();
        }
    }, 30);  }