What is cross browser support for JavaScript 1.7's new features? Specifically array comprehensions and the “let” statement

Question

https://developer.mozilla.org/en/New_in_JavaScript_1.7

A lot of these new features are borrowed from Python, and would allow the creation of less verbose apps, which

Answer 1

No, when they say "JavaScript", they mean it literally: the ECMAScript engine used by Gecko. JScript and other engines (AFAIK) don't support these features.

EDIT: According to wikipedia, JavaScript 1.7 implements ECMAScript "Edition 3 plus all JavaScript 1.6 enhancements, plus Pythonic generators and array comprehensions ([a*a for (a in iter)]), block scope with let, destructuring assignment (var [a,b]=[1,2])". So these features are not part of ECMAScript.