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Comment by altrego99 | Hacker News Reader

This is sweet. Also because I love what they are doing on javascript development. For example,

1. Destructuring references is not yet supported on Chrome

  [a,b,c]=[c,d,f]
  [a,b]=[b,a+b]

2. Shorthand functions are sweet

  [1,2,3,4].map(function(x) x*x)) // [1,4,9,16]

3. Chrome doesn't have an inbuilt shell (Shift+F4 in Firefox)

Granted CoffeeScript makes some of these easy, but they are too paranoid in my opinion to support new and useful syntaxes (e.g. yield keyword for generators, getters/setters).

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Shorthand functions are not standard yet. You should bet on arrow function expressions in Harmony for now:

  [1,2,3,4].map(x => x*x)) // [1,4,9,16]

(also note that |this| is lexically bound in the case of fat arrow functions)

Also, destructuring objects:

  let obj = { foo: 42, bar: { baz: 32 } }
  let { foo, bar } = obj;
  foo // 42
  bar.baz // 32

https://developer.mozilla.org/en-US/docs/Web/JavaScript/New_...

List of all the goodies: https://developer.mozilla.org/en-US/docs/Web/JavaScript/New_...

edit: formatting

Which Firefox version does the arrow syntax (=>) work on? It's not working on my 21.0.

Firefox 22.

I haven't used Firefox seriously in a while, but the shift+F4 shortcut looks fairly similarly to the Chrome developer console (F12, select the Console tab). It looks like the Firefox shell is more designed for making new pages though, while the Chrome one is more for debugging the current page.

I use Firefox, and I had no idea about Shift+F4 either. Firefox also has Ctrl-Shift-K (probably Cmd-Shift-K on Mac) which is much more similar to the Chrome console you're talking about, and is useful for debugging the page you're on.

>Destructuring references is not yet supported on Chrome

Eh. Yea, Firefox got support for that (and `let` and generators/iterators), because they added it in 2006 (Firefox 2.0) as an experimental feature.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/New_...

I didn't know about that function syntax. Does it work just like the arrow function syntax?

    [1,2,3,4].map(x => x * x) // [1,4,9,16]

I wonder why they included two new shorter function syntax alternatives. Is one of them recommended/deprecated?

one is standard the other is not.

This doesn't seem to work on Firefox 21 shell. Does it work on FF 22?

Yep, it seems it was added on Firefox 22: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe.... It also seems it's the proposal for ES6: http://wiki.ecmascript.org/doku.php?id=harmony:arrow_functio....

This blog post explains the differences between these functions and current functions: http://javascriptweblog.wordpress.com/2012/04/09/javascript-...; i wish the unbound "->" alternative is included, so that functions used as methods can also use the new syntax.

Which Firefox version does this syntax work on? It's not working on my 21.0.

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