ECMAScript for XML

ECMAScript for XML (E4X) is a programming language extension that adds native XML support to ECMAScript (JavaScript). It does this by providing access to the XML document in a form that feels natural for ECMAScript programmers. The goal is to provide an alternative, simpler syntax for accessing XML documents than via DOM interfaces. Additionally, it offers a new way of visualizing XML. Up to the release of E4X XML was always accessed at an object level. E4X changes that, and thinks of XML as a primitive (equivalent to a character, integer, or boolean). This implies faster access, better support, and acceptance as a building block (data structure) of a program.

E4X is standardized by Ecma International in ECMA-357 standard. The first edition was published in June 2004, the second edition in December 2005.

Implementations

E4X is implemented (at least partially) in SpiderMonkey (Gecko's JavaScript engine) and in Rhino.

As Mozilla Firefox is based on Gecko, it can be used to run scripts using E4X. The specification is relatively new and is only supported in the 1.5 release or later. For more information about using E4X in Mozilla-based browsers, see [1].

Macromedia's ActionScript 3 scripting language fully supports E4X and will available to developers later in 2005. For more information about this, see [2].

Resources

• Tutorial from W3 Schools
• ECMA-357 standard
• E4X at faqts.com
• Slides from E4X Presentation by Brendan Eich, Mozilla Chief Architect