Question about GetBindingValue
sukyoung.ryu at gmail.com
Fri Aug 29 18:21:00 PDT 2014
Thank you all for your answers! Your answers were really helpful.
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 (22.214.171.124.6 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.
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