[Bug 27122] MutationObserver.observe(node, {}) should throw

https://www.w3.org/Bugs/Public/show_bug.cgi?id=27122

--- Comment #10 from Jonas Sicking <jonas@sicking.cc> ---
(In reply to Olli Pettay from comment #7)
> if observe(foo, { ... something...}) doesn't end up doing anything (not
> observe any changes), that should throw. Scripts should know asap that
> something is going wrong, not wait later to figure out that the expected
> MutationRecords won't be there.

You seem to consider "observing fewer things than expected" to be different
from "observing nothing". Is that true?

I.e. in both of

MutationObserver.observe(node, { newFeature: true })
MutationObserver.observe(node, { newFeature: true, childList: true })

the newFeature observations won't be fired in a downlevel browser. Are you
saying that's worse in the first case than in the second case?

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Received on Tuesday, 21 October 2014 22:49:10 UTC