https://github.com/heycam/webidl/pull/356 removed custom hasInstance behavior in 2017, and the feature has only been shipped by Firefox.
Dropping the support means that JavaScript `instanceof` operator will return false when the contexts of the object and the constructor don't match, e.g. the object is from an iframe and the constructor is from the top window. The change will initially be only on Nightly to make sure there won't be any significant breakages, and then will propagate to stable versions. Tracking bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1360715 WPT: https://wpt.live/WebIDL/ecmascript-binding/has-instance.html Relevant flag: dom.webidl.crosscontext_hasinstance.enabled _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
