Function tryParseDatePattern

ark/type/keywords/string.ts:229–267

(
	data: string,
	opts?: DateOptions
)

	`a ${format}-formatted date`

export const tryParseDatePattern = (
	data: string,
	opts?: DateOptions
): Date | string => {
	if (!opts?.format) {
		const result = new Date(data)
		return isValidDateInstance(result) ? result : "a valid date"
	}
	if (opts.format === "iso") {
		return iso8601Matcher.test(data) ?
				new Date(data)
			:	writeFormattedExpected("iso")
	}
	const dataParts = data.split(dayDelimiterMatcher)
	// will be the first delimiter matched, if there is one
	const delimiter: string | undefined = data[dataParts[0].length]
	const formatParts = delimiter ? opts.format.split(delimiter) : [opts.format]

	if (dataParts.length !== formatParts.length)
		return writeFormattedExpected(opts.format)

	const parsedParts: ParsedDayParts = {}
	for (let i = 0; i < formatParts.length; i++) {
		if (
			dataParts[i].length !== formatParts[i].length &&
			// if format is "m" or "d", data is allowed to be 1 or 2 characters
			!(formatParts[i].length === 1 && dataParts[i].length === 2)
		)
			return writeFormattedExpected(opts.format)

		parsedParts[formatParts[i][0] as PartKey] = dataParts[i]
	}

	const date = new Date(`${parsedParts.m}/${parsedParts.d}/${parsedParts.y}`)

	if (`${date.getDate()}` === parsedParts.d) return date

	return writeFormattedExpected(opts.format)
}

const isParsableDate = (s: string) => !Number.isNaN(new Date(s).valueOf())