Re: Mutation Events and Null values

>In order to be DOM-compliant, are prevValueArg, newValueArg and
attrNameArg
>required to be non-null for those MutationEvent types for which they
apply?

Yes.

>It seems like supporting this requirement for prevValue could degrade
>overall UA performance

In general mutation events are a performance challenge simply because
they're so pervasive and uncontrolled. You can  do some things with
partially deferred computation, or with suppressing events unless there are
active listeners; I believe Xerces' implementation demonstrates a few
simple ideas along those lines.




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Joe Kesselman  / IBM Research