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events: optimize various functions
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Cache events and listeners objects where possible and loop over
Object.keys() instead of using for..in. These changes alone give
~60-65% improvement in the ee-add-remove benchmark.

The changes to EventEmitter.listenerCount() gives ~14%
improvement and changes to emitter.listeners() gives
significant improvements for <50 listeners
(~195% improvement for 10 listeners).

The changes to emitter.emit() gives 3x speedup for the fast
cases with multiple handlers and a minor speedup for the slow
case with multiple handlers.

The swapping out of the util.is* type checking functions with inline
checks gives another ~5-10% improvement.

PR-URL: #601
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Evan Lucas <evanlucas@me.com>
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mscdex authored and bnoordhuis committed Feb 9, 2015
1 parent c86e383 commit b677b84
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2 comments on commit b677b84

@tsbehlman
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for...in is much faster for objects as plain as the events object. The Object.keys() method is only faster if you would otherwise need to rely on hasOwnProperty. See this jsPerf. I can back this up with a benchmark suite running in io.js 1.1.0.

Update: I just pulled the changes and compared the added use of Object.keys to an equivalent for...in and found no significant difference in performance as reported by the events benchmarks.

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@mscdex mscdex commented on b677b84 Feb 10, 2015

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@tsbehlman See the discussion about that in the original PR here.

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