Status: New
Owner: ----
New issue 2743 by [email protected]: `in` operator performance
http://code.google.com/p/v8/issues/detail?id=2743
A common use case for the `in` operator (as well as
`Object#hasOwnProperty`) is to check if a certain value is part of a set of
values, represented by an object.
As long as ES6's `Set` isn't enabled by default, it would be great if V8
could speed this up, so that the `in` operator has similar performance
characteristics as a direct property accesses (eg. possibly by adding it to
ICs?).
I've got two projects using this excessively,
https://github.com/fb55/htmlparser2 and
https://github.com/fb55/readabilitySAX . The latter is based on the former,
and it usually spends ~5% of it's time evaluating the `in` operator (tested
with various pages; the easiest check would probably be
https://github.com/fb55/readabilitySAX/blob/master/tests/test_performance.js).
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