Unscopeable

Andreas Rossberg rossberg at google.com
Wed Aug 21 07:07:22 PDT 2013


On 21 August 2013 15:41, Erik Arvidsson <erik.arvidsson at gmail.com> wrote:
> One way to think of it is that the with is acting on a view of the
> object that does not have the blacklisted properties. This can be
> implemented using proxies. I'll leave that as an exercise.

I see.

>> * How would it interact with mutation?
>
> Another hole we didn't cover. Here is my proposal:
>
> The @@unscopable is only accessed once, when the object environment
> record is created.

Hm, that would seem rather inconsistent with the way adding/removing
properties can dynamically change the domain of a 'with'. Consider:

  function safeenrich(o) {
    o.a = 1
    o[@@unscopable] = o[@@unscopable] || []
    o[@@unscopable].push('a')
  }

  let o = {}
  let a = 0
  with (o) {
    a  // 0
    safeenrich(o)
    a  // 1
  }

/Andreas


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