Add formatRfc7231 function

Author: fabon-f

CHANGELOG.md

@@ -9,7 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-- `startOfYear`, `startOfMonth`, `startOfDay`, `startOfHour`, `startOfMinute`, `startOfSecond`, `endOfYear`, `endOfMonth`, `endOfDay`, `endOfHour`, `endOfMinute`, `endOfSecond`, `fromRfc2822`, `fromRfc7231` functions
+- `startOfYear`, `startOfMonth`, `startOfDay`, `startOfHour`, `startOfMinute`, `startOfSecond`, `endOfYear`, `endOfMonth`, `endOfDay`, `endOfHour`, `endOfMinute`, `endOfSecond`, `fromRfc2822`, `fromRfc7231`, `formatRfc7231` functions
 
 ### Changed
 

src/datetime/_getMonthAbbreviationFromNumber.test.ts

@@ -0,0 +1,18 @@
+import { expect, test } from "vitest";
+
+import { getMonthAbbreviationFromNumber } from "./_getMonthAbbreviationFromNumber.js";
+
+test("getMonthAbbreviationFromNumber", () => {
+	expect(getMonthAbbreviationFromNumber(1)).toEqual("Jan");
+	expect(getMonthAbbreviationFromNumber(2)).toEqual("Feb");
+	expect(getMonthAbbreviationFromNumber(3)).toEqual("Mar");
+	expect(getMonthAbbreviationFromNumber(4)).toEqual("Apr");
+	expect(getMonthAbbreviationFromNumber(5)).toEqual("May");
+	expect(getMonthAbbreviationFromNumber(6)).toEqual("Jun");
+	expect(getMonthAbbreviationFromNumber(7)).toEqual("Jul");
+	expect(getMonthAbbreviationFromNumber(8)).toEqual("Aug");
+	expect(getMonthAbbreviationFromNumber(9)).toEqual("Sep");
+	expect(getMonthAbbreviationFromNumber(10)).toEqual("Oct");
+	expect(getMonthAbbreviationFromNumber(11)).toEqual("Nov");
+	expect(getMonthAbbreviationFromNumber(12)).toEqual("Dec");
+});

src/datetime/_getMonthAbbreviationFromNumber.ts

@@ -0,0 +1,20 @@
+export function getMonthAbbreviationFromNumber(num: number): string {
+	const name = [
+		"Jan",
+		"Feb",
+		"Mar",
+		"Apr",
+		"May",
+		"Jun",
+		"Jul",
+		"Aug",
+		"Sep",
+		"Oct",
+		"Nov",
+		"Dec",
+	][num - 1];
+	if (name === undefined) {
+		throw new Error(`Invalid month number: ${num}`);
+	}
+	return name;
+}

src/datetime/formatRfc7231.test.ts

@@ -0,0 +1,25 @@
+import { Temporal } from "@js-temporal/polyfill";
+import { expect, test } from "vitest";
+
+import { formatRfc7231 } from "./formatRfc7231.js";
+
+test("ZonedDateTime", () => {
+	expect(
+		formatRfc7231(
+			Temporal.ZonedDateTime.from("2024-06-07T10:23:45+09:00[Asia/Tokyo]"),
+		),
+	).toEqual("Fri, 07 Jun 2024 01:23:45 GMT");
+	expect(
+		formatRfc7231(
+			Temporal.ZonedDateTime.from(
+				"2024-06-07T10:23:45+09:00[Asia/Tokyo][u-ca=hebrew]",
+			),
+		),
+	).toEqual("Fri, 07 Jun 2024 01:23:45 GMT");
+});
+
+test("Instant", () => {
+	expect(formatRfc7231(Temporal.Instant.from("2024-06-07T01:23:45Z"))).toEqual(
+		"Fri, 07 Jun 2024 01:23:45 GMT",
+	);
+});

src/datetime/formatRfc7231.ts

@@ -0,0 +1,25 @@
+import { isInstant } from "../type-utils.js";
+import type { Temporal } from "../types.js";
+import { getDayOfWeekAbbreviationFromNumber } from "./_getDayOfWeekAbbreviationFromNumber.js";
+import { getMonthAbbreviationFromNumber } from "./_getMonthAbbreviationFromNumber.js";
+
+/**
+ * Returns a string in RFC 7231's format which represents an exact time of given temporal object.
+ *
+ * @param dt temporal object which includes exact time info (`Instant` and `ZonedDateTime`)
+ * @returns a string formatted according to RFC 7231
+ */
+export function formatRfc7231(
+	dt: Temporal.Instant | Temporal.ZonedDateTime,
+): string {
+	// timeZone: 'UTC', calendar: 'iso8601'
+	const zdt = (isInstant(dt) ? dt : dt.toInstant()).toZonedDateTimeISO("UTC");
+	const dayOfWeek = getDayOfWeekAbbreviationFromNumber(zdt.dayOfWeek);
+	const year = zdt.year.toString().padStart(4, "0");
+	const day = zdt.day.toString().padStart(2, "0");
+	const month = getMonthAbbreviationFromNumber(zdt.month);
+	const hour = zdt.hour.toString().padStart(2, "0");
+	const minute = zdt.minute.toString().padStart(2, "0");
+	const second = zdt.second.toString().padStart(2, "0");
+	return `${dayOfWeek}, ${day} ${month} ${year} ${hour}:${minute}:${second} GMT`;
+}

src/datetime/index.ts

@@ -15,6 +15,7 @@ export { endOfMinute } from "./endOfMinute.js";
 export { endOfMonth } from "./endOfMonth.js";
 export { endOfSecond } from "./endOfSecond.js";
 export { endOfYear } from "./endOfYear.js";
+export { formatRfc7231 } from "./formatRfc7231.js";
 export {
 	formatWithoutLocale,
 	type FormatWithoutLocaleOptions,