`this`: methods versus functions

Brendan Eich brendan at mozilla.com
Wed Nov 9 16:00:07 PST 2011


On Nov 9, 2011, at 3:48 PM, Axel Rauschmayer wrote:

>>> Or are there other plans to get it solved? I would still love to see that happen, it’s a remarkably subtle source of errors. Could functions adopt the block-lambda semantics of picking up the `this` of the surrounding scope when not invoked as methods? It seems like that could work in strict mode where no one expects `this` to have a value.
>> 
>> No, if you call such functions via object.method() references then this binds to object. You can't break such compatibility only at runtime, and only some of the time.
> 
> Got it. I’m assuming that’s a performance issue?

You could say that. If we inherit by default but it's a "soft binding", then the inner function has to carry that reference with it, but in a way that can be overridden.

We talked about lexical this for functions long ago (Jan. 2008? at Google anyway) and IIRC Mark found a subtler flaw.

/be



More information about the es-discuss mailing list