{"action":"created","issue":{"url":"https://api.github.com/repos/RByers/EventListenerOptions/issues/2","labels_url":"https://api.github.com/repos/RByers/EventListenerOptions/issues/2/labels{/name}","comments_url":"https://api.github.com/repos/RByers/EventListenerOptions/issues/2/comments","events_url":"https://api.github.com/repos/RByers/EventListenerOptions/issues/2/events","html_url":"https://github.com/RByers/EventListenerOptions/issues/2","id":92777179,"number":2,"title":"Is modifying the value of cancelable OK?","user":{"login":"RByers","id":1280419,"avatar_url":"https://avatars.githubusercontent.com/u/1280419?v=3","gravatar_id":"","url":"https://api.github.com/users/RByers","html_url":"https://github.com/RByers","followers_url":"https://api.github.com/users/RByers/followers","following_url":"https://api.github.com/users/RByers/following{/other_user}","gists_url":"https://api.github.com/users/RByers/gists{/gist_id}","starred_url":"https://api.github.com/users/RByers/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/RByers/subscriptions","organizations_url":"https://api.github.com/users/RByers/orgs","repos_url":"https://api.github.com/users/RByers/repos","events_url":"https://api.github.com/users/RByers/events{/privacy}","received_events_url":"https://api.github.com/users/RByers/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/RByers/EventListenerOptions/labels/spec","name":"spec","color":"fbca04"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":12,"created_at":"2015-07-03T02:34:03Z","updated_at":"2015-07-10T19:30:16Z","closed_at":null,"body":"It's a little weird to say that 'Event.cancelable' changes value in the context of a particular handler.  The alternative of an event being uncancelable only when ALL handlers have asked for that seems worse though.  I guess we could describe this as the handler getting a mutated copy of the event?  But that would be annoying (possibly expensive) to implement and probably impossible to polyfill.\r\n"},"comment":{"url":"https://api.github.com/repos/RByers/EventListenerOptions/issues/comments/120502724","html_url":"https://github.com/RByers/EventListenerOptions/issues/2#issuecomment-120502724","issue_url":"https://api.github.com/repos/RByers/EventListenerOptions/issues/2","id":120502724,"user":{"login":"dtapuska","id":10406468,"avatar_url":"https://avatars.githubusercontent.com/u/10406468?v=3","gravatar_id":"","url":"https://api.github.com/users/dtapuska","html_url":"https://github.com/dtapuska","followers_url":"https://api.github.com/users/dtapuska/followers","following_url":"https://api.github.com/users/dtapuska/following{/other_user}","gists_url":"https://api.github.com/users/dtapuska/gists{/gist_id}","starred_url":"https://api.github.com/users/dtapuska/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/dtapuska/subscriptions","organizations_url":"https://api.github.com/users/dtapuska/orgs","repos_url":"https://api.github.com/users/dtapuska/repos","events_url":"https://api.github.com/users/dtapuska/events{/privacy}","received_events_url":"https://api.github.com/users/dtapuska/received_events","type":"User","site_admin":false},"created_at":"2015-07-10T19:30:16Z","updated_at":"2015-07-10T19:30:16Z","body":"I agree with @smaug---- that the event shouldn't mutate; but we should send a clone of it so if somebody holds a reference we are ok.\r\n\r\nRoughly... \r\n\r\nnode.addEventListener('foo', function (event) {\r\n   window.firstEvent = event;\r\n},  { mayCancel: true});\r\nnode.addEventListener('foo', function (event) {\r\n   // querying window.firstEvent should be the same as it was when first dispatched...\r\n},  { mayCancel: false});\r\n\r\n"}}