js中转换布局格式为绝对定位

<script>
window.onload = function () {
var oUl = document.getElementById('ul1');
var aLi = oUl.getElementsByTagName('li');
var i = 0;
//获取网页布局的数值
for (i = 0; i < aLi.length; i++) {
aLi[i].style.left = aLi[i].offsetLeft + 'px';
aLi[i].style.top = aLi[i].offsetTop + 'px';
}
//转换为绝对定位
for (i = 0; i < aLi.length; i++) {
aLi[i].style.position = 'absolute';
aLi[i].style.margin = '0';
}
};
</script>