Merge pull request #53 from bjuppa/rework-formatInstant

Rework format instant
bjuppa · Jul 4, 2023 · fe93971 · fe93971
2 parents 2781e9e + 116a1b4
commit fe93971
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Showing 2 changed files with 35 additions and 6 deletions.
diff --git a/utils/formatInstant.ts b/utils/formatInstant.ts
@@ -8,8 +8,8 @@ export type FormatInstantOptions = Omit<Intl.DateTimeFormatOptions, "timeZone">;
  * 1. `Intl` {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl#locales_argument | locale },
  *    defaults to system's locale if not given.
  * 2. `Intl` {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat/DateTimeFormat | format options },
- *    defaults to include a "short" timezone-style if no options given.
- * 3. A named IANA timezone.
+ *    defaults to include a "short" timezone-style unless `timeZoneName` is explicitly `undefined`.
+ * 3. A named IANA timezone, defaults to system's timezone if not given.
  *
  * @param locale `Intl` locale,
  * @returns A curried function that takes `Intl` format options and returns another curried function that takes a timezone and returns the final curried function that operates on JS `Date` objects
@@ -25,11 +25,12 @@ export type FormatInstantOptions = Omit<Intl.DateTimeFormatOptions, "timeZone">;
  * format24hDateTime(new Date());  // "6/11/2023, 16:54:32"
  * ```
  */
-export function formatInstant(locale: Intl.LocalesArgument = undefined): (
+export function formatInstant(locale?: Intl.LocalesArgument): (
   options?: FormatInstantOptions,
-) => (timezone: string) => (instant: Date) => string {
+) => (timezone?: string) => (instant: Date) => string {
   return (options = { timeZoneName: "short" }) => (timezone) => (instant) =>
     instant.toLocaleString(locale, {
+      timeZoneName: "short",
       ...options,
       timeZone: timezone,
     });

diff --git a/utils/formatInstant_test.ts b/utils/formatInstant_test.ts
@@ -27,13 +27,41 @@ Deno.test("takes Intl options", () => {
   );
 });
 
-Deno.test("ignores timezone in options", () => {
+Deno.test("adds timeZoneName to options if left out", () => {
+  const instant = new Date("2023-06-10T13:20:30+0100");
+  assertEquals(
+    formatInstant("en")({ hourCycle: "h23" })("Europe/London")(
+      instant,
+    ),
+    "6/10/2023, 13:20:30 GMT+1",
+  );
+});
+
+Deno.test("doesn't add timeZoneName when explicitly set to undefined", () => {
+  const instant = new Date("2023-06-10T13:20:30+0100");
+  assertEquals(
+    formatInstant("en")({ timeZoneName: undefined })("Europe/London")(
+      instant,
+    ),
+    "6/10/2023, 1:20:30 PM",
+  );
+});
+
+Deno.test("ignores timeZone in options", () => {
   const instant = new Date("2023-06-10T13:20:30+0100");
   assertEquals(
     // @ts-ignore: Pass timeZone even if not allowed by type
     formatInstant("en")({ timeZone: "America/Chicago" })("Europe/London")(
       instant,
     ),
-    "6/10/2023, 1:20:30 PM",
+    "6/10/2023, 1:20:30 PM GMT+1",
+  );
+});
+
+Deno.test("accepts leaving all parameters empty for system defaults and short timezone name", () => {
+  const instant = new Date("2023-06-10T13:20:30+0100");
+  assertEquals(
+    formatInstant()()()(instant),
+    instant.toLocaleString(undefined, { timeZoneName: "short" }),
   );
 });