Replace for/push loop with Array of initial size

[edemaine]

I noticed this bit of code which builds an array via push incrementally instead of just calling map. I believe map is faster because it can pre-allocate an array of the right size. This jsbench confirms my hypothesis. The code is also shorter and cleaner.

Or is map being avoided on purpose for compatibility? It's ECMAScript 5. MDN; Can I use.

[discussion on Discord]

[coveralls]

Pull Request Test Coverage Report for Build 2164463861

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.004%) to 89.563%

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Totals
Change from base Build 2147526457:	0.004%
Covered Lines:	1217
Relevant Lines:	1296

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💛 - Coveralls

[ryansolid]

Hmm.. I tested this a lot before. For wasn't only faster it was like 30% faster in my benchmarks. When I was struggling to get the fastest SSR this one of the blockers that led me to creating a separate runtime for server. Then I looked at what Marko was doing and using for + push was the key.

I'm sort of surprised map is faster. It never has been historically, but it's worth reviewing.

Also Chrome 100 is a bit crazy right now. It sort of broke a bunch of the benchmarks. I think we need to test in a V8 node server environment.

[edemaine]

liquid on Discord pointed out that

• The map version is slower for large arrays (for me, the crossover point is around 20 items), and
• There's a for-loop version that is the best of both worlds: preallocate an Array of the correct size. Here's the new benchmark. It's faster for arrays of size 1, 4, 20, etc.

I pushed code for the new version.

[ryansolid]

Thank you.