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

While this question is a bit old, and is marked "answered" - I found it on Google and the answers given are possibly inaccurate, or if not, definitely incomplete.

It's very important to note that Javascript is NOT A STANDARD. Ken correctly mentioned that ECMAScript is the cross-browser standard that all browsers aim to comply with, but what he didn't clarify is that Javascript is NOT ECMAScript.

To say Javascript "implements" ECMAScript means that Javascript includes ECMAScript, plus it's own proprietary extra non-cross-browser features. The for each example given by nicholas is an example of a proprietary feature added by Mozilla that is not in any standard, and therefore unlikely to be adopted by any other browsers.

Javascript 1.7 and 1.8 features are useful for extension development in XUL, but should never be used for cross-browser development - that's what standards are for.