ECMAScript for XML (E4X) is a programming language extension that adds native XML support to ECMAScript (which includes ActionScript, DMDScript, JavaScript, JScript). The goal is to provide an alternative to DOM interfaces that uses a simpler syntax for accessing XML documents. It also offers a new way of making XML visible. Before the release of E4X, XML was always accessed at an object level. E4X instead treats XML as a primitive (like characters, integers, and booleans). This implies faster access, better support, and acceptance as a building block (data structure) of a program.
E4X is standardized by Ecma International in the ECMA-357 standard. The first edition was published in June 2004, the second edition in December 2005.
var sales = <sales vendor="John"> <item type="peas" price="4" quantity="6"/> <item type="carrot" price="3" quantity="10"/> <item type="chips" price="5" quantity="3"/> </sales>; alert( sales.item.(@type == "carrot").@quantity ); alert( sales.@vendor ); for each( var price in sales..@price ) { alert( price ); } delete sales.item[0]; sales.item += <item type="oranges" price="4"/>; sales.item.(@type == "oranges").@quantity = 4;
The first implementation of E4X was designed by Terry Lucas and John Schneider and appeared in BEA's Weblogic Workshop 7.0 released in February 2002. BEA's implementation was based on Rhino and released before the ECMAScript E4X spec was completed in June 2004. John Schneider wrote an article on the XML extensions in BEA's Workshop at the time. The reference documentation for this pre-E4X language is still available.