perf: avoid array iterators over objects

[GalacticHypernova]

Object iterators like Object.keys, Object.values, and Object.entries, when used for iteration, create a temporary intermediate array by internally making another iteration, essentially doubling the memory usage and execution time. Using object iterators will avoid that intermediate array and the extra internal iteration.

Benchmark (each section ran separately to prevent any inline cache from altering results):

const largeObject = {}
for (let i=0; i<100000;i++) {
    largeObject[i] = i
}

console.time("array method")
for (const num of Object.keys(largeObject)) {
    // It doesn't matter what happens within the loop as the main slowdown is the keys iterator
}
console.timeEnd("array method")

console.time("obj method")
for (const num in largeObject) {
    // It doesn't matter what happens within the loop as the main slowdown is the keys iterator
}
console.timeEnd("obj method")

Performance results:

Memory results:

In places where prototype pollution may be a concern, a review would be appreciated so I could add own property checks

[pkg-pr-new]

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@vue/compiler-core

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@vue/compiler-dom

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@vue/compiler-sfc

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@vue/reactivity

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@vue/runtime-core

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@vue/runtime-dom

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@vue/server-renderer

pnpm add https://pkg.pr.new/@vue/server-renderer@12264

@vue/shared

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vue

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@vue/compat

pnpm add https://pkg.pr.new/@vue/compat@12264

commit: 3123a16

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	100 kB (-13 B)	38 kB (-2 B)	34.2 kB (+42 B)
vue.global.prod.js	159 kB (-13 B)	57.9 kB (-2 B)	51.4 kB (-13 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	46.9 kB	18.3 kB	16.7 kB
createApp	55 kB	21.3 kB	19.4 kB
createSSRApp	59 kB	23 kB	20.9 kB
defineCustomElement	59.7 kB (-13 B)	22.8 kB (-3 B)	20.8 kB (-70 B)
overall	68.7 kB	26.3 kB	24 kB

[edison1105]

a side note:
ctx.modelDecls and ctx.userImports are usually not large objects.