fix: eliminate use of instanceof

[goldsam]

Description:
Eliminate use of instanceof to support passing observables between javascript contexts

Related issue (if exists):
Closes #2628

[coveralls]

Coverage increased (+0.001%) to 97.736% when pulling 3c62bd6 on goldsam:trans-js-context-support into 279d775 on ReactiveX:master.

[kwonoj]

Leving comment for fyi: let's discussion continues on issue itself at #2628.

[benlesh]

Given that the workaround for the corner case issue this is solving is a simple Observable.from, I'm opposed to this change unless we can prove there's no performance impact.

Adding a function call, 2 property lookups, 2 typeof's and 3 assertions, instead of a single instanceof check everywhere we want to assert that it's our Observable instance? Seems extreme to solve a rare problem.

[benlesh]

Given the lack of action on this, and my general disagreement, I'm going to close this issue for now.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.