arrow function syntax simplified

Brendan Eich brendan at
Thu Mar 29 12:02:18 PDT 2012

Brendan Eich wrote:
> Irakli Gozalishvili wrote:
>> Few questions on this new arrow functions:
>> let foo = x => x * x
>> 1. What is foo.prototype ?
>> 2. What does new foo(y) does ?
> The idea with arrow function syntax (as opposed to block-lambda 
> revival) was to be as close to "just syntax" for functions. Obviously 
> we've made early-error restrictions but this design goal still stands. 
> So the answers are:
> 1. Same as for any user-defined function (a fresh Object instance).
> 2. Same as for any user-defined function. 

Oops, I left off something important. Since we agreed on lexical |this| 
binding, there's no way for the new object to flow into the arrow 
function. So I'm wrong, the answers are:

1. Same as for any built-in function: no .prototype property at all.
2. Arrow-functions lack [[Construct]] so you cannot 'new' them.

This makes arrows like built-ins. They're still functions, per my other 

I'll update the strawman (which should be promoted shortly).

Thanks for the good questions!


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