DOM 解析中的浏览器差异

所有现代浏览器都支持 W3C DOM 规范。

不过，浏览器之间是有差异的。重要的区别有两点：

• 加载 XML 的方式
• 处理空白和换行的方式

在 “解析 XML DOM” 这一节，已经解释了加载 XML 的不同方式。

在本节中，我们将讲解处理空白和换行的不同方式。

DOM - 空白和换行

XML 经常在节点之间含有换行或空白字符。这是在使用简单的编辑器（比如记事本）时经常出现的情况。

下面的例子（由记事本编辑）在每行之间含有 CR/LF，在每个子节点之前含有两个空格：

<book>
  <title>Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>

Firefox，以及其他一些浏览器，会把空的空白或换行作为文本节点来处理，而 Internet Explorer 不会这样。

下面的代码片段显示 （books.xml 的） 根元素拥有多少个子节点：

xmlDoc=loadXMLDoc("books.xml");

x=xmlDoc.documentElement.childNodes;
document.write("Number of child nodes: " + x.length);

例子解释：

• 通过使用 loadXMLDoc() 把 "books.xml" 载入 xmlDoc 中
• 获取根元素的子节点
• 输出子节点数目

结果取决于所使用的浏览器。Firefox 输出 9，而 IE 输出 4。

TIY

忽略节点间的空文本

如需忽略元素节点之间的空文本节点，需要检查节点类型。元素节点的类型是 1：

xmlDoc=loadXMLDoc("books.xml");

x=xmlDoc.documentElement.childNodes;

for (i=0;i<x.length;i++)
{ 
if (x[i].nodeType==1)
  {// only process element nodes 
  document.write(x[i].nodeName);
  document.write("<br />");
  } 
}

例子解释：

• 通过使用 loadXMLDoc() 把 "books.xml" 载入 xmlDoc 中
• 获取根元素的子节点
• 检查每个子节点的节点类型。如果节点类型是 "1"，则是元素节点

TIY（简单） 或者 TIY（完整）

英文解 释：MSDN JScript Reference: The escape method returns a string value (in Unicode format) that contains the contents of [the argument].

All spaces, punctuation, accented characters, and any other non- ASCII characters are replaced with %xx encoding, where xx is equivalent to the hexadecimal number representing the character.

For example, a space is returned as "%20."

Edge Core Javascript Guide: The escape and unescape functions let you encode and decode strings.

The escape function returns the hexadecimal encoding of an argument in the ISO Latin character set.

The unescape function returns the ASCII string for the specified hexadecimal encoding value.

英文解 释：MSDN JScript Reference: The encodeURI method returns an encoded URI.

If you pass the result to decodeURI, the original string is returned.

The encodeURI method does not encode the following characters: ":", "/", ";", and "?".

Use encodeURIComponent to encode these characters. Edge Core Javascript Guide: Encodes a Uniform Resource

Identifier (URI) by replacing each instance of certain characters by one, two, or three escape sequences representing the UTF- 8 encoding of the character

英文解 释：MSDN JScript Reference: The encodeURIComponent method returns an encoded URI. If you pass the result to decodeURIComponent, the original string is returned.

Because the encodeURIComponent method encodes all characters, be careful if the string represents a path such as /folder1 /folder2 /default.html. The slash characters will be encoded and will not be valid if sent as a request to a web server. Use the encodeURI method if the string contains more than a

single URI component. Mozilla Developer Core Javascript Guide： Encodes a Uniform Resource Identifier (URI) component by replacing each instance of certain characters by one,

two, or three escape sequences representing the UTF- 8 encoding of the character.

英文注 释：The escape() method does not encode the + character which is interpreted as a space on the server side as well as generated by forms with spaces in their fields.

Due to this shortcoming, you should avoid use of escape() whenever possible. The best alternative is usually encodeURIComponent().

Use of the encodeURI() method is a bit more specialized than escape() in that it encodes for URIs [REF] as opposed to the querystring,

which is part of a URL. Use this method when you need to encode a string to be used for any resource that uses URIs and needs certain characters to remain un- encoded. Note that this method does not encode the ' character, as it is a valid character within URIs.Lastly, the encodeURIComponent() method should be used in most

cases when encoding

a single component of a URI. This method will encode certain chars that would normally be recognized as special chars for URIs so that many components may be included.

Note that this method

does not encode the ' character, as it is a valid character within URIs.