Though the ECMA working group hasn’t issued a new specification
array methods such as
lastIndexOf, as well as iterators
(methods to help one move through, or iterate through, a collection such
as an array):
More, there’s no guarantee that Microsoft will concur with the steps that the Mozilla organization is taking with the language enhancements. However, unlike the issues with different interpretations of the DOM, which was the primary cause of cross-browser difficulties in past JS lives, we’re now faced with a growing separation in the basic programming language itself.