previousSibling用法注意

定义和用法

previousSibling 属性返回选定节点的上一个同级节点（在相同树层级中的前一个节点）。

如果不存在这样的节点，则该属性返回 null。

注意：

var y=get_previoussibling(x);

代码实例中前面加上了（get_）

语法：

elementNode.previousSibling

实例

在所有的例子中，我们将使用 XML 文件 books.xml，以及 JavaScript 函数 loadXMLDoc()。

  <?xml version="1.0" encoding="ISO-8859-1" ?> 
- <!--   Copyright w3school.com.cn 
  --> 
- <!--  W3School.com.cn bookstore example 
  --> 
- <bookstore>
- <book category="children">
  <title lang="en">Harry Potter</title> 
  <author>J K. Rowling</author> 
  <year>2005</year> 
  <price>29.99</price> 
  </book>
- <book category="cooking">
  <title lang="en">Everyday Italian</title> 
  <author>Giada De Laurentiis</author> 
  <year>2005</year> 
  <price>30.00</price> 
  </book>
- <book category="web" cover="paperback">
  <title lang="en">Learning XML</title> 
  <author>Erik T. Ray</author> 
  <year>2003</year> 
  <price>39.95</price> 
  </book>
- <book category="web">
  <title lang="en">XQuery Kick Start</title> 
  <author>James McGovern</author> 
  <author>Per Bothner</author> 
  <author>Kurt Cagle</author> 
  <author>James Linn</author> 
  <author>Vaidyanathan Nagarajan</author> 
  <year>2003</year> 
  <price>49.99</price> 
  </book>
  </bookstore>

下面的代码片段获取 XML 文档中第一个 <author> 元素的上一个同级节点：

<html>
<head>
<script type="text/javascript" src="/example/xdom/loadxmldoc.js"> 
</script>
</head>
<body>
<script type="text/javascript">
//check if the previous sibling node is an element node
function get_previoussibling(n)
{
var x=n.previousSibling;
while (x.nodeType!=1)
  {
  x=x.previousSibling;
  }
return x;
}

xmlDoc=loadXMLDoc("/example/xdom/books.xml");

var x=xmlDoc.getElementsByTagName("author")[0];
document.write(x.nodeName);
document.write(" = ");
document.write(x.childNodes[0].nodeValue);

var y=get_previoussibling(x);

document.write("<br />Previous sibling: ");
document.write(y.nodeName);
document.write(" = ");
document.write(y.childNodes[0].nodeValue);
</script>
</body>
</html>

输出

author = J K. Rowling
Previous sibling: title = Harry Potter

nextSibling——获取节点的下一个同级节点

<html>
<head>
<script type="text/javascript" src="/example/xdom/loadxmldoc.js"> 
</script>
</head>
<body>
<script type="text/javascript">
//check if the next sibling node is an element node
function get_nextsibling(n)
{
var x=n.nextSibling;
while (x.nodeType!=1)
  {
  x=x.nextSibling;
  }
return x;
}

xmlDoc=loadXMLDoc("/example/xdom/books.xml");

var x=xmlDoc.getElementsByTagName("title")[0];
document.write(x.nodeName);
document.write(" = ");
document.write(x.childNodes[0].nodeValue);

var y=get_nextsibling(x);

document.write("<br />Next sibling: ");
document.write(y.nodeName);
document.write(" = ");
document.write(y.childNodes[0].nodeValue);
</script>
</body>
</html>

输出

title = Harry Potter
Next sibling: author = J K. Rowling