+21 bytes

This only fixes the issue in IE, not Edge. See the comment at#4435 (comment) for the rationale.

We could also accept the perf hit & assign such a temporary name attribute in all browsers, at least once. Hopefully that wouldn't cause style recalculation as the final value would be the same as the initial one, worth checking.

PR updated.

I build a test case similar tohttps://jsbin.com/cocaqis/1/edit?html,js but with one iframe being available immediately in the DOM (with similar DOM contents) and another similar one being added after a few seconds. If there was no workaround, all of them failed. If I added a workaround in the main doc, all succeeded. If I added one in the first iframe, the selection in the main DOM failed & then the selection in both iframes succeeded. If I added it to the second one, it was failing until the selection happened in that second iframe, then all started suceeding.

Also, if I see success, after refreshing the page (with "Always refresh from server" checked in the Network DevTools tab) I see every selection succeeding as well so the workaround even survives page refreshes.

Of course, IE being IE, it's not impossible that the workaround stops working after a while but for now I think we can work on the assumption it survives long enough. If that proves not enough, we'll depend on someone submitting an issue.

+30 bytes, BTW.

Sizzle version of the PR:jquery/sizzle#461

PR updated.[name=''] now falls back to Sizzle traversal & both IE 11 & Edge 15-18 pass all tests.+49 +50 bytes.