ECMAscript for XML

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Draft

ECMAscript for XML (ak E4X) is an extension to ECMAscript.

It is available in

• Some JavaScript engines, e.g.
  • Firefox SpiderMonkey (the default JS engine)
• ActionScript 3

Using E4X is considerably simpler than using the DOM. Maybe some day we will be back to the elegance of languages like LISP instead of fighting against obscure C/Java syntax.....

Usage patterns

Creating an E4X XML object

(1) The easiest way is to create a new variable and just create the XML structure like this. In ECMAScript 4 (e.g. ActionScript 3) you should define the type of the variable.

var instructions:XML  = <stepbystep>
  <doctitle></doctitle>
  <steps>
    <title></title>
  </steps>
 </stepbystep>;

Don't forget the ";" at the end since this instruction extends over several lines.

(1b) In JavaScript 1.6 (ECMAScript 3) you can't define types and you simply use:

 var instructions  = <stepbystep> ....

This the same principle as creating an array or an object like this:

 var arr = [item1,item2,item3];
 var obj = {a:"item 1",b:"item 2",c:"item 3"}

(2) You also can create an XML E4X object from a string with the new XML() constructor.

var instruction_string = "<stepbystep>

 <doctitle></doctitle>
 <steps>
   <title></title>
 </steps>
</stepbystep>";

var instruction2:XML = new XML(instruction_string);

(3) Computing expressions

to do: {...}

XML lists

XML lists are the other important datastructure in E4X. Lists are needed for example to hold results of queries (like NodeLists in the DOM model).

Here is a little example of an XML list:

    <step>
      <title>step 1</title>
    </step>
    <step>
      <title>step 2</title>
    </step>
    <step>
      <title>step 3</title>
    </step>

Accessing elements and attributes

Again, there is a similarity between E4X objects, arrays, and traditional Object.

(1) Using the "." syntax

Let's take an example:

var steps:XML =
 <stepbystep>   
  <doctitle>Sample document</doctitle>
  <info>
    <para>See <a href="http://edutechwiki.unige.ch/en/ECMAscript_for_XML">ECMAscript for XML</a></para>
  </info>
  <steps>
    <title>List of steps</title>
    <step>
      <title>step 1</title>
    </step>
    <step>
      <title>step 2</title>
    </step>
    <step>
      <title>step 3</title>
      <para>That was easy !</para>
    </step>
  </steps>
 </stepbystep>;

A little example

• Story (look at the source of this file)

Links

Overviews

• ECMAScript for XML (Wikipedia)

Introductions and tutorials

JavaScript

• Fremantle, Paul and Anthony Elder (1005). AJAX and scripting Web services with E4X, Part 1, IBM Works, HTML

• E4X Tutorial, W3Schools.

• Introducing E4X (by Kurt Cagle, xml.com, nov 2007)

• E4X by Mark. Useful as short manual !

• At Mozilla (Firefox)
  • E4X Tutorial (Mozilla Developer center)
  • Processing XML with E4X (JavaScript 1.6 +)
  • E4X, Mozilla Developer Center.

Flash/ActionScript/Flex

• The E4X approach to XML processing (Adobe, part of the Flex manual/Programming ActionScript 3.0)

• Using an E4X expression in a data binding expression (Adobe)

• E4X (Adobe, Flex, Getting Started)

• Intro to E4X (Actionscript.org) by Hasan Otuome

Php

• PHP5 quick database E4X queries (Adobe, Flex cookbook) by Sand Wyrm.

Namespaces

• How does E4X deal with XML with namespaces? by Martin Honnen (2005)
• How can I access elements or attributes that are in a namespace? by Martin Honnen (2005)

Standard and Manuals

• ECMA-357 standard
• E4X Short tutorial by Mark. Also useful as short manual !