function getStyle(obj,attr) {
            return obj.currentStyle ? obj.currentStyle[attr] : getComputedStyle(obj)[attr];
        }
        function startMove(obj,attr,target) {
            clearInterval(obj.timer);
            obj.timer = setInterval(function () {
                // 返回的字符串，需转换成number类型
                // var curAttr = parseInt(getStyle(obj,attr));
                // var curAttr = (attr == 'opacity') ? parseFloat(getStyle(obj,attr))*100 : parseInt(getStyle(obj,attr));
                var curAttr = (attr == 'opacity') ? parseInt(parseFloat(getStyle(obj,attr))*100) : parseInt(getStyle(obj,attr));
                var speed = (target - curAttr)/8;
                speed = speed > 0 ? Math.ceil(speed) : Math.floor(speed);
                if (curAttr == target) {    //是否到达终点
                    clearInterval(obj.timer);
                } else {
                    if (attr == 'opacity') {
                        curAttr += speed;
                        obj.style.opacity = (curAttr + speed)/100;
                        obj.style.filter = 'alpha(opacity:' + (curAttr + speed) + ')';
                        document.getElementById('txt').value = obj.style.opacity;
                    } else {
                        obj.style[attr] = curAttr + speed + 'px';
                    }
                }
            },300);
        }