兄弟节点
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>JS</title>
</head>
<body>
<div id="box">
<button class="btn">按钮</button>
<span id="span">
<a href="#">百度一下</a>
</span>
<p>我是段落</p>
</div>
<script type="text/javascript">
window.onload = function() {
var span = document.getElementById("span");
//上一个兄弟节点
var previous = span.previousElementSibling || span.previousSibling;
console.log(previous);
//下一个兄弟节点
var dom = span.nextElementSibling || span.nextSibling;
console.log(dom);
}
</script>
</body>
</html>