</head>
<body>
<script>
windows.onload = function () {
var oDiv = document.getElementById('list');
var aUl = oDiv.getElementsByTagName('ul');
var aLi = null;
for (var i = 0; i<aUl.length; i++) {
aLi = aUl[i].getElementsByTagName('li');
for (var i = 0; i<aLi.length; i++) {
aLi[i].style.border = "1px solid #f00"
}
}
}
</script>
代码aUl[i]在for循环里引用aUl.length.length指的是ul标签的个数.aUl[i].length这样就是第几个标签的长度了.aUl.length当时这里指明了第几个ul,aUl.length这个是全部ul的个数