Add toTemporalFromClockTime function

Author: fabon-f

src/datetime/_formatDateIso.ts

@@ -0,0 +1,19 @@
+export function formatDateIso(date: Date) {
+	const year = date.getFullYear().toString();
+	const month = (date.getMonth() + 1).toString().padStart(2, "0");
+	const day = date.getDate().toString().padStart(2, "0");
+	const hour = date.getHours().toString().padStart(2, "0");
+	const minute = date.getMinutes().toString().padStart(2, "0");
+	const second = date.getSeconds().toString().padStart(2, "0");
+	const millisecond = date.getMilliseconds().toString().padStart(3, "0");
+
+	const offset = date.getTimezoneOffset();
+
+	const offsetHours = Math.floor(Math.abs(offset) / 60)
+		.toString()
+		.padStart(2, "0");
+	const offsetMinutes = (Math.abs(offset) % 60).toString().padStart(2, "0");
+	const offsetString = `${offset > 0 ? "-" : "+"}${offsetHours}:${offsetMinutes}`;
+
+	return `${year}-${month}-${day}T${hour}:${minute}:${second}.${millisecond}${offsetString}`;
+}

src/datetime/index.ts

@@ -7,3 +7,4 @@ export { isAfter } from "./isAfter.js";
 export { isBefore } from "./isBefore.js";
 export { latest } from "./latest.js";
 export { toDateFromClockTime } from "./toDateFromClockTime.js";
+export { toTemporalFromClockTime } from "./toTemporalFromClockTime.js";

src/datetime/toTemporalFromClockTime.test.ts

@@ -0,0 +1,49 @@
+import { Temporal } from "@js-temporal/polyfill";
+import { expect, test } from "vitest";
+
+import { toTemporalFromClockTime } from "./toTemporalFromClockTime.js";
+
+test("to PlainDate", () => {
+	expect(
+		toTemporalFromClockTime(
+			new Date("2024-01-01T00:00:00"),
+			Temporal.PlainDate,
+		),
+	).toEqual(Temporal.PlainDate.from("2024-01-01"));
+});
+
+test("to PlainTime", () => {
+	expect(
+		toTemporalFromClockTime(
+			new Date("2024-01-01T00:00:00"),
+			Temporal.PlainTime,
+		),
+	).toEqual(Temporal.PlainTime.from("00:00:00"));
+});
+
+test("to PlainDateTime", () => {
+	expect(
+		toTemporalFromClockTime(
+			new Date("2024-01-01T00:00:00"),
+			Temporal.PlainDateTime,
+		),
+	).toEqual(Temporal.PlainDateTime.from("2024-01-01T00:00:00"));
+});
+
+test("to PlainYearMonth", () => {
+	expect(
+		toTemporalFromClockTime(
+			new Date("2024-01-01T00:00:00"),
+			Temporal.PlainYearMonth,
+		),
+	).toEqual(Temporal.PlainYearMonth.from("2024-01"));
+});
+
+test("to PlainMonthDay", () => {
+	expect(
+		toTemporalFromClockTime(
+			new Date("2024-01-01T00:00:00"),
+			Temporal.PlainMonthDay,
+		),
+	).toEqual(Temporal.PlainMonthDay.from("01-01"));
+});

src/datetime/toTemporalFromClockTime.ts

@@ -0,0 +1,23 @@
+import type { Temporal } from "../types.js";
+import { formatDateIso } from "./_formatDateIso.js";
+
+/**
+ * Returns Temporal instance which represents clock (local) time of given date.
+ * @param date `Date` object
+ * @param TemporalClass Temporal class (such as `Temporal.Plaindate`) which will be returned
+ * @returns an instance of Temporal class specified in `temporalClass` argument, which represents the clock time of original date
+ */
+export function toTemporalFromClockTime<
+	TemporalClassType extends
+		| typeof Temporal.PlainDate
+		| typeof Temporal.PlainTime
+		| typeof Temporal.PlainDateTime
+		| typeof Temporal.PlainYearMonth
+		| typeof Temporal.PlainMonthDay,
+>(
+	date: Date,
+	TemporalClass: TemporalClassType,
+): InstanceType<TemporalClassType> {
+	const dateIso = formatDateIso(date);
+	return TemporalClass.from(dateIso) as InstanceType<TemporalClassType>;
+}