175802 2017-08-21 17:48:46 -0700 RTCPeerConnection addEventListener handler context changed (a new this?) 2017-11-09 01:31:16 -0800 1 1 1 Unclassified WebKit UI Events Safari Technology Preview Mac macOS 10.12.4 NEW InRadar P2 Normal --- 1 jiali.passion webkit-unassigned cdumez eric.carlson marcel mroberts webkit-bug-importer youennf oldest_to_newest 1340878 0 jiali.passion 2017-08-21 17:48:46 -0700 The reproduce code is below. <html> <head> <script> window.onload = function () { console.log('Create RTCPeerConnection') const pc = new RTCPeerConnection() console.log('Add "track" event listener') pc.addEventListener('track', function(_event) { console.log('this === pc', this === pc); console.log('track event', _event); }); console.log('Dispatch "track" event') pc.dispatchEvent(new Event('track')) } </script> </head> </html> the output will be ------------------------ this === pc, false in the eventhandler of `track`, the context `this` is different with `pc`. In Firefox and Chrome, this is the same with pc. 1340919 1 mroberts 2017-08-21 19:11:23 -0700 I can confirm this happens for apparently any event dispatched to RTCPeerConnection (all WebRTC-related events and even arbitrary events like "foo"). 1341556 2 webkit-bug-importer 2017-08-23 09:12:07 -0700 <rdar://problem/34035850>