javascript

Chapter 16: ECMA Script for XML
so it inherits all of the default properties and methods of all objects. There are a few ways to create a new
XML object, the first of which is to call the constructor like this:
var x = new XML();
This line creates an empty XML object that can be filled with data. You can also pass in an XML string to
the constructor as shown in this example:
var x = new XML(“ < employee position=\”Software Engineer\” > < name > Nicholas “ +
“Zakas < /name > < /employee > ”);
The XML string passed into the constructor is parsed into an object hierarchy of XML objects.
Additionally, you can pass in a DOM document or node to the constructor as follows and have its data
represented in E4X:
var x = new XML(xmldom);
Even though these methods of construction are useful, the most powerful and interesting method is
direct assignment of XML data into a variable via an XML literal. XML literals are nothing more than
XML code embedded into JavaScript code. Here ’ s an example:
var employee = < employee position=”Software Engineer” >
< name > Nicholas C. Zakas < /name >
< /employee > ;
Here, an XML data structure is assigned directly to a variable. This augmented syntax creates an XML
object and assigns it to the employee variable.
The Firefox implementation of E4X doesn ’ t support the parsing of XML prologs. If
< ?xml version= “ 1.0 ” ? > is present, either in text that is passed to the XML
constructor or as part of the XML literal, a syntax error occurs.
The toXMLString() method returns an XML string representing the object and its children. The
toString() method, on the other hand, behaves differently based on the contents of the XML object. If
the contents are simple (plain text), then the text is returned; otherwise toString() acts the same as
toXMLString() . Consider the following example:
var data = < name > Nicholas C. Zakas < /name > ;
alert(data.toString()); //” > Nicholas C. Zakas”
alert(data.toXMLString()); //” < name > Nicholas C. Zakas < /name > ”
Between these two methods, most XML serialization needs can be met.
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