Check whether date is valid in getDayOfWeekFromYmd helper

Author: fabon-f

src/datetime/_formatDateIso.ts

@@ -1,30 +1,3 @@
-import { formatExactTimeIso } from "./_formatExactTimeIso.js";
-
-export function formatDateIso(date: Date) {
-	const year = date.getFullYear();
-	const month = date.getMonth() + 1;
-	const day = date.getDate();
-	const hour = date.getHours();
-	const minute = date.getMinutes();
-	const second = date.getSeconds();
-	const millisecond = date.getMilliseconds();
-
-	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}:${offsetMinutes}`;
-
-	return formatExactTimeIso(
-		year,
-		month,
-		day,
-		hour,
-		minute,
-		second,
-		millisecond,
-		offsetString,
-	);
+export function formatDateIso(year: number, month: number, day: number) {
+	return `${year.toString()}-${month.toString().padStart(2, "0")}-${day.toString().padStart(2, "0")}`;
 }

src/datetime/_formatExactTimeIso.ts

@@ -1,3 +1,5 @@
+import { formatDateIso } from "./_formatDateIso.js";
+
 export function formatExactTimeIso(
 	year: number,
 	month: number,
@@ -8,12 +10,9 @@ export function formatExactTimeIso(
 	millisecond: number,
 	offsetString: string,
 ) {
-	const yearStr = year.toString();
-	const monthStr = month.toString().padStart(2, "0");
-	const dayStr = day.toString().padStart(2, "0");
 	const hourStr = hour.toString().padStart(2, "0");
 	const minuteStr = minute.toString().padStart(2, "0");
 	const secondStr = second.toString().padStart(2, "0");
 	const millisecondStr = millisecond.toString().padStart(3, "0");
-	return `${yearStr}-${monthStr}-${dayStr}T${hourStr}:${minuteStr}:${secondStr}.${millisecondStr}${offsetString}`;
+	return `${formatDateIso(year, month, day)}T${hourStr}:${minuteStr}:${secondStr}.${millisecondStr}${offsetString}`;
 }

src/datetime/_formatIsoFromDateObject.ts

@@ -0,0 +1,30 @@
+import { formatExactTimeIso } from "./_formatExactTimeIso.js";
+
+export function formatIsoFromDateObject(date: Date) {
+	const year = date.getFullYear();
+	const month = date.getMonth() + 1;
+	const day = date.getDate();
+	const hour = date.getHours();
+	const minute = date.getMinutes();
+	const second = date.getSeconds();
+	const millisecond = date.getMilliseconds();
+
+	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 formatExactTimeIso(
+		year,
+		month,
+		day,
+		hour,
+		minute,
+		second,
+		millisecond,
+		offsetString,
+	);
+}

src/datetime/_getDayOfWeekFromYmd.test.ts

@@ -22,6 +22,15 @@ test("result of getDayOfWeekFromYmd should match to Temporal's dayOfWeek", () =>
 	);
 });
 
+test("invalid date", () => {
+	expect(() => {
+		getDayOfWeekFromYmd(2024, 1, 366);
+	}).toThrowError();
+	expect(() => {
+		getDayOfWeekFromYmd(2023, 2, 29);
+	}).toThrowError();
+});
+
 test("getDayOfWeekFromYmd with a day which doesn't exist in local time zone", () => {
 	zoneModifier.set("Pacific/Apia");
 	// 2011/12/30 was skipped in Pacific/Apia due to offset change (UTC-11:00 -> UTC+13:00)

src/datetime/_getDayOfWeekFromYmd.ts

@@ -1,6 +1,16 @@
+import { formatDateIso } from "./_formatDateIso.js";
+
 /**
  * same as temporal's spec, Monday: 1, Tuesday: 2, ... Sunday: 7
  */
 export function getDayOfWeekFromYmd(year: number, month: number, day: number) {
-	return ((new Date(Date.UTC(year, month - 1, day)).getUTCDay() + 6) % 7) + 1;
+	const date = new Date(Date.UTC(year, month - 1, day));
+	if (
+		date.getUTCFullYear() !== year ||
+		date.getUTCMonth() !== month - 1 ||
+		date.getUTCDate() !== day
+	) {
+		throw new Error(`Invalid date: ${formatDateIso(year, month, day)}`);
+	}
+	return ((date.getUTCDay() + 6) % 7) + 1;
 }

src/datetime/toTemporalFromClockTime.ts

@@ -1,5 +1,5 @@
 import type { Temporal } from "../types.js";
-import { formatDateIso } from "./_formatDateIso.js";
+import { formatIsoFromDateObject } from "./_formatIsoFromDateObject.js";
 
 /**
  * Returns Temporal instance which represents clock (local) time of given date.
@@ -18,6 +18,6 @@ export function toTemporalFromClockTime<
 	date: Date,
 	TemporalClass: TemporalClassType,
 ): InstanceType<TemporalClassType> {
-	const dateIso = formatDateIso(date);
+	const dateIso = formatIsoFromDateObject(date);
 	return TemporalClass.from(dateIso) as InstanceType<TemporalClassType>;
 }