Allen Wirfs-Brock (2014-11-25T16:11:33.000Z)
d at domenic.me (2014-12-04T22:35:08.322Z)
On Nov 25, 2014, at 2:14 AM, Anne van Kesteren wrote: > On Tue, Nov 25, 2014 at 1:51 AM, Allen Wirfs-Brock > <allen at wirfs-brock.com> wrote: >> There is definite a 1:1:1 relationship between a global object, realmRec, >> global environment record. And ES views those relationships are immutable. >> You can't just change the global object of a realmRec or give it a different >> global environment record after it has been initialized. > > How would you test whether all three of them have changed? Changed in what sense and from what perspective? Every ES function object is associated with a realm when the function object is created. That association can't be changed as it would violated internal invariants of the function. For example: function f() { let gPO = Object.getPrototypeOf; let a = gPO( [ ] ); doSomething(); let b = gPO( [ ] ); assert(a===b); } The "current realm" dynamically tracks the realm of the actively executing ES function. The only way to change the "current realm" is to transfer control (via call, return, throw) to a function that was created with a different realm association. regarding var document = someDocument.open(...); perhaps you can model this by saying that every Document object is created in a new Realm. Then the `open` call is a cross-realm call that changes the current Realm to someDocument's realm. When `open` returns the current Realm is restored to the original caller's realm. `document` is just a property of the caller realm's global object so the assignment just changes the value of that property. Any subsequent method invocations on 'document' will be cross-realm calls into someDocument's realm.