Yes, it's async so that could indeed explain why you see 2,3,2
But I don't get why the notifications are not grouped together using the tag property like on Android. Here, it says that Safari on iOS also supports it.
My guess would be there is some difference in the API for replacing notifications.
Ohhh, I think I found the error.
Let me guess. If I reply three times to you, you only get a single notification which shows "you have 3 new replies", right?
Let this be the first reply.
reply
Second reply.
reply
Third reply.
Please tell me you only got one notification haha
If so, I am pretty sure what is causing the bug
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I got 3 notifications
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damn
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Same. I don't think there's any grouping happening on iOS.
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Created a question on SO now
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Someone replied that this may indeed be a bug in WebKit. Filed a bug report with them now: https://bugs.webkit.org/show_bug.cgi?id=258922