The goal of this revision was to update the ECMAScript specification to reflect the language as it is actually implemented in modern web browsers and to establish a foundation for the future evolutions of the language. New features include accessor properties, reflective creation and inspection of objects, program control of property attributes, additional array manipulation functions, support for the JSON object encoding format, and a strict mode that provides enhanced error checking and program security. Many of these features standardize enhanced functionality that has been provided by individual browsers but has not yet been universally adopted.
So, what does it mean for this to be a “candidate specification”? All the contributors to this development wanted to make sure that revising the ECMAScript specification would improve the web for developers. To this end, we all committed to not finalizing a revision unless it had first been demonstrated that the revision can be interoperably implemented by web browsers and that such implementations can continue to compatibility handle existing web content. The “candidate specification” is the specification revision that is going to be tested against those requirements. Having reached the “candidate specification” milestone means that all features are frozen and that we are done with specification writing. Microsoft and others are already well along with prototype implementations that will be used for testing. We all hope and expect that the testing will be successful and completed by the end of this summer so that the ECMAScript Fifth Edition can be ratified as an official web standard by the end of this year.
For the average web developer the release of a candidate specification has little immediate impact because you have to create content that works with the browser versions that are actually in use today. However, we expect that once it is finally approved, the revised ECMAScript standard to be widely and fairly rapidly adopted by browsers. In the meantime, this new specification is already having an impact. For example, in IE8 both the native JSON and the DOM Prototypes features are based upon APIs defined in the ECMAScript Fifth Edition Specification.
Microsoft Representatives to ECMA TC-39
Co-project Editors, ECMAScript Fifth Edition Specification