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ECMAScript for XML

Note that even though this example is syntactically correct, it causes an error in browsers other than

Mozilla when it is executed because neither function (defineGetter() or

defineSetter()

) is defined.

Microsoft

Microsoft hasn’t updated its browser-based implementation of JavaScript since Internet Explorer 5.5 was

released. What it has done, however, is include a language called JScript.NET in the .NET Framework.

JScript.NET is, for all intents and purposes, an implementation of ECMAScript Edition 4 with some

Microsoft-specific additions added for good measure. However, it can’t be used as a client-side scripting

language in Internet Explorer, only as a server-side language in ASP.NET or as a standalone application

(yes, JScript.NET can be compiled).

Unlike other versions of JavaScript, JScript.NET is a compiled language capable of becoming a stan-

dalone executable file. It is compiled down to the same .NET machine code and executed using the

same Common Language Runtime (CLR) as both Visual Basic.NET and C#. Although it is beyond the

scope of this book to discuss the full potential and scope of JScript.NET, more information is available

on Microsoft’s Web site at

http://msdn.microsoft.com/library/en-us/dnclinic/html/

scripting07142000.asp?frame=true

ECMAScript for XML

In 2002, a group of companies led by BEA Systems proposed an extension to ECMAScript to add native

XML support to the language. At that point, XML was starting to gain popularity, and the companies

wanted to make sure that ECMAScript was in the forefront of this next technology wave. In June 2004,

ECMAScript for XML (E4X) was released as ECMA-357. E4X is not its own language; rather, as origi-

nally intended, it is an optional extension to the ECMAScript language. As such, E4X introduces new

syntax for dealing with XML, as well as for XML-specific objects.

Approach

E4X stays away from implementing the current XML standards, such as SAX, XPath, and DOM, and

instead presents a unique way of creating and manipulating XML documents. The E4X approach

takes aspects from technologies such as DOM, XPath, and XSLT, although it doesn’t map specifically

to either one.

For example, suppose you were dealing with the following XML code:

<name>Nicholas C. Zakas</name>

</employee>

<name>Jim Smith</name>

</employee>

</employees>

This XML could be assigned to an ECMAScript variable by using the following code:

var oXml = <employees>

<name>Nicholas C. Zakas</name>

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