window.onload = function () {

/*var ali = document.getElementsByTagName('li'); // 获取LI

           for (var i = 0; i < ali.length; i++) {

               ali[i].timer = null; //使用数组写法定义独立的定时器，避免公用定时器的争抢。

               ali[i].onmouseover = function () {

                   stratMove(this, 400);

               }

               ali[i].onmouseout = function () {

                   stratMove(this, 200);

               }

           }

       }*/

var Li1 = document.getElementById('li1');

//var Li2 = document.getElementById('li2');

Li1.onmouseover = function () {

startMove(this, 'opacity',100);

}

Li1.onmouseout = function () {

stratMove(this, 'opacity', 30);

}

}

//var timer = null; //定义一个定时器,取消公用定时器

var alpha = 30;

function startMove(obj, attr, iTarget) {

clearInterval(obj.timer);

obj.timer = setInterval(function () {

var icur = 0;

if (attr == 'opacity') {

//Math.round()将一个数四舍五入为一个最接近的整数

icur = Math.round(parseFloat(getStyle(obj, attr)) * 100);

} else {

icur = parseInt(getStyle(obj, attr));

}

var speed = (iTarget - icur) / 8;

speed = speed > 0 ? Math.ceil(speed) : Math.floor(speed);

if (icur == iTarget) {

clearInterval(obj.timer);

} else {

if (attr == 'opacity') {

obj.style.filter = 'alpha(opacity('+(icur+speed)+')';

obj.style.opacity = (icur + speed) / 100;

} else {

obj.style[attr] = icur + speed;

}

}

}, 30);

}

function getStyle(obj, attr) {

if (obj.currentStyle) {

return obj.currentStyle[attr];

} else {

return getComputedStyle(obj, false)[attr];

}

} //封装获取样式元素