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<body><span class="vcard"><a class="email" href="mailto:cdumez@apple.com" title="Chris Dumez <cdumez@apple.com>"> <span class="fn">Chris Dumez</span></a>
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<a class="bz_bug_link
bz_status_NEW "
title="NEW - I found one more onbeforeunload event return value coercion edge case"
href="https://bugs.webkit.org/show_bug.cgi?id=169789">bug 169789</a>
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<td>cdumez@apple.com
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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - I found one more onbeforeunload event return value coercion edge case"
href="https://bugs.webkit.org/show_bug.cgi?id=169789#c1">Comment # 1</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - I found one more onbeforeunload event return value coercion edge case"
href="https://bugs.webkit.org/show_bug.cgi?id=169789">bug 169789</a>
from <span class="vcard"><a class="email" href="mailto:cdumez@apple.com" title="Chris Dumez <cdumez@apple.com>"> <span class="fn">Chris Dumez</span></a>
</span></b>
<pre>(In reply to <a href="show_bug.cgi?id=169789#c0">comment #0</a>)
<span class="quote">> The newly-introduced test at
> <a href="http://w3c-test.org/html/browsers/browsing-the-web/unloading-documents/">http://w3c-test.org/html/browsers/browsing-the-web/unloading-documents/</a>
> beforeunload-canceling.html named
>
> > Returning false must not cancel the event, because it's coerced to the DOMString "false" which does not cancel CustomEvents: CustomEvent, cancelable
>
> does not pass in Safari Tech Preview 25. Everything else does (except the
> test "Returning a string must not cancel the event: BeforeUnloadEvent with
> type "click", cancelable" which is fine since it's best if Safari doesn't
> implement createEvent("beforeunload"); see
> <a href="https://github.com/whatwg/dom/issues/362">https://github.com/whatwg/dom/issues/362</a>.)</span >
I am not clear yet on what part of the spec says so.
I found:
<a href="https://html.spec.whatwg.org/#the-event-handler-processing-algorithm">https://html.spec.whatwg.org/#the-event-handler-processing-algorithm</a> (step 5)
which says:
If return value is not null, then:
1. Set E's canceled flag.
...
So if you return false, we cancel the event.</pre>
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