Run results for: Intl.DateTimeFormat formatToParts vs. format then regex

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.2.1 Safari/605.1.15

Browser: Safari 17

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: 2 years ago

Benchmark engine: Benchmark.js

Test name	Executions per second
✓ dtf.format	583,438 Ops/sec
hackyOffset	521,894 Ops/sec
dtf.formatToParts	402,348 Ops/sec
partsOffset	251,861 Ops/sec

Script Preparation code:

jsDate = new Date()

dtf = new Intl.DateTimeFormat("en-US", {
	hour12: false,
	timeZone: "America/New_York",
	year: "numeric",
	month: "2-digit",
	day: "2-digit",
	hour: "2-digit",
	minute: "2-digit",
	second: "2-digit",
	era: "short",
})

// from luxon
function hackyOffset(dtf, date) {
	const formatted = dtf.format(date).replace(/\u200E/g, ""),
		parsed = /(\d+)\/(\d+)\/(\d+) (AD|BC),? (\d+):(\d+):(\d+)/.exec(formatted),
		[, fMonth, fDay, fYear, fadOrBc, fHour, fMinute, fSecond] = parsed ?? []
	return [fYear, fMonth, fDay, fadOrBc, fHour, fMinute, fSecond]
}

const typeToPos = {
	year: 0,
	month: 1,
	day: 2,
	era: 3,
	hour: 4,
	minute: 5,
	second: 6,
}

function partsOffset(dtf, date) {
	const formatted = dtf.formatToParts(date)
	const filled = []
	for (let i = 0; i < formatted.length; i++) {
		const { type, value } = formatted[i]
		const pos = typeToPos[type]

		if (type === "era") {
			filled[pos] = value
		} else if (pos !== undefined) {
			filled[pos] = parseInt(value, 10)
		}
	}
	return filled
}