Question about GetBindingValue

Sukyoung Ryu sukyoung.ryu at gmail.com
Fri Aug 29 18:21:00 PDT 2014


Thank you all for your answers!  Your answers were really helpful.

Best,
--
Sukyoung


On Aug 30, 2014, at 12:34 AM, Allen Wirfs-Brock wrote:

> 
> On Aug 29, 2014, at 4:07 AM, André Bargull wrote:
> 
>> ...
>> 
>>> We checked with the recent ES6 draft but it seems to have the same issue.
>> 
>> In ES6 it's actually possible to reach that step (8.1.1.2.6 GetBindingValue, step 5), albeit it's a somewhat tricky and involves doing unusual things with proxy objects:
>> 
>> ,,,
>> Proxy objects allow you to define your own [[HasProperty]] implementation (the "has" method in the example above). In this case [[HasProperty]] will return `true` on the first call in order to report a binding is present in HasBinding, but then will return `false` when the binding's presence is checked the second time in GetBindingValue.
>> 
> 
> And in ES5, host object have similar capabilities.  I believe we put this checks in specifically to make sure everything was well defined in the presence of such host objects.
> 
> Allen
> 



More information about the es-discuss mailing list