The standard published under the dry title ECMA-262, 5th Edition hereafter referred to as ES5, is the latest version of the ECMAScript specification. ECMAScript is the standard upon which JavaScript—the single most important language on the web today—is built. Because the language also serves as the basis for Adobe ActionScript in addition to other flavors, it’s fair to say that the ECMAScript standard is central to the present and future of interactivity on the web.
Published in December 2009, ES5 represents an incremental improvement in the language, arrived at through a lengthy, and occasionally contentious, process. Still, whatever friction there might have been in the development of the specification, the end result contains some excellent enhancements to the language. This article outlines the long history of the specification’s development, then steps through many of its important new features and concepts.