iterator microbenchmark shootout

iterators.mjs

const { baseline, bench, run } = await import('https://esm.sh/mitata')

const data = Array.from(Array(1000).map(() => Math.random()))

bench('for {0;<;++} data[i]', () => {
	let sum = 0
	for (let i = 0; i < data.length; ++i) {
		sum += data[i]
	}
	return sum
})

bench('for-of', () => {
	let sum = 0
	for (const x of data) {
		sum += x
	}
	return sum
})

bench('for-of keys()', () => {
	let sum = 0
	for (const i of data.keys()) {
		sum += data[i]
	}
	return sum
})

bench('for-of values()', () => {
	let sum = 0
	for (const x of data.values()) {
		sum += x
	}
	return sum
})

bench('forEach', () => {
	let sum = 0
	data.forEach((x) => {
		sum += x
	})
	return sum
})

bench('reduce', () => {
	const sum = data.reduce((x, y) => x + y, 0)
	return sum
})

bench('iterator object', () => {
	let sum = 0
	const length = data.length
	const e = {
		[Symbol.iterator]: () => {
			let i = 0
			return {
				next: () => ({
					done: i >= length,
					value: data[i++],
				}),
			}
		},
	}
	for (const x of e) {
		sum += x
	}
	return sum
})

bench('generator wrapping for {0;<;++}}', () => {
	let sum = 0
	const custom_iter = {
		[Symbol.iterator]: function* () {
			let i = 0
			for (i = 0; i < data.length; ++i) {
				yield data[i]
			}
		},
	}
	for (const x of custom_iter) {
		sum += x
	}
	return sum
})

bench('wrapped generator (for-of yield)', () => {
	let sum = 0
	const custom_iter = (function* () {
		let x
		for (x of data.values()) {
			yield x
		}
	})()
	for (const x of custom_iter) {
		sum += x
	}
	return sum
})

bench('delegated generator (yield* data.values())', () => {
	const custom_iter2 = (function* () {
		yield* data.values()
	})()
	let sum = 0
	for (const x of custom_iter2) {
		sum += x
	}
	return sum
})

await run({
	avg: true, // enable/disable avg column (default: true)
	json: false, // enable/disable json output (default: false)
	colors: false, // enable/disable colors (default: true)
	min_max: false, // enable/disable min/max column (default: true)
	collect: true, // enable/disable collecting returned values into an array during the benchmark (default: false)
})