按层次关系访问结点

<script type="text/javascript">
function showNode( ){
    var imgObj=document.getElementById("imgFruit");
    var  imgParent=imgObj.parentNode;
    alert(imgParent.nodeName);
    
    var  bodyFirstChild=imgParent.firstChild   ;
    alert(bodyFirstChild.nodeName);
    
    var  bodyLastChild=imgParent.lastChild  ;
    alert(bodyLastChild.nodeName);
}
</script>
<title>DOM节点</title>
</head>
<body>
    <img src="images/fruit.jpg" alt="图片" id="imgFruit" />
    <h1>喜欢的水果</h1>
    <input type="button" onclick="showNode()" value="查找节点"/>
    <p>DOM应用</p>
</body>