refactor: re-write timeAgo() to use Intl.DurationFormat (#706)

Author: iuioiua

utils/display.ts

@@ -1,20 +1,15 @@
 // Copyright 2023-2025 the Deno authors. All rights reserved. MIT license.
-import { difference } from "$std/datetime/difference.ts";
+import { difference, type Unit } from "$std/datetime/difference.ts";
 
-/**
- * Returns a pluralized string for the given amount and unit.
- *
- * @example
- * ```ts
- * import { pluralize } from "@/utils/display.ts";
- *
- * pluralize(0, "meow"); // Returns "0 meows"
- * pluralize(1, "meow"); // Returns "1 meow"
- * ```
- */
-export function pluralize(amount: number, unit: string) {
-  return amount === 1 ? `${amount} ${unit}` : `${amount} ${unit}s`;
-}
+const units = [
+  "years",
+  "months",
+  "weeks",
+  "days",
+  "hours",
+  "minutes",
+  "seconds",
+] as Unit[];
 
 /**
  * Returns how long ago a given date is from now.
@@ -28,29 +23,15 @@ export function pluralize(amount: number, unit: string) {
  * timeAgo(new Date(Date.now() - 3 * HOUR)); // Returns "3 hours ago"
  * ```
  */
-export function timeAgo(date: Date) {
+export function timeAgo(date: Date): string {
   const now = new Date();
   if (date > now) throw new Error("Timestamp must be in the past");
-  const match = Object.entries(
-    difference(now, date, {
-      // These units make sense for a web UI
-      units: [
-        "seconds",
-        "minutes",
-        "hours",
-        "days",
-        "weeks",
-        "months",
-        "years",
-      ],
-    }),
-  )
-    .toReversed()
-    .find(([_, amount]) => amount > 0);
-  if (match === undefined) return "just now";
-  const [unit, amount] = match;
-  // Remove the last character which is an "s"
-  return pluralize(amount, unit.slice(0, -1)) + " ago";
+  const duration = difference(date, now, { units });
+  if (duration.seconds === 0) return "just now";
+  const largestUnit = units.find((unit) => duration[unit]! > 0) || "seconds";
+  // @ts-ignore - TS doesn't know about this API yet
+  return new Intl.DurationFormat("en", { style: "long" })
+    .format({ [largestUnit]: duration[largestUnit] }) + " ago";
 }
 
 /**

utils/display_test.ts

@@ -1,14 +1,8 @@
 // Copyright 2023-2025 the Deno authors. All rights reserved. MIT license.
-import { formatCurrency, pluralize, timeAgo } from "./display.ts";
+import { formatCurrency, timeAgo } from "./display.ts";
 import { DAY, HOUR, MINUTE, SECOND } from "$std/datetime/constants.ts";
 import { assertEquals, assertThrows } from "$std/assert/mod.ts";
 
-Deno.test("[display] pluralize()", () => {
-  assertEquals(pluralize(0, "item"), "0 items");
-  assertEquals(pluralize(1, "item"), "1 item");
-  assertEquals(pluralize(2, "item"), "2 items");
-});
-
 Deno.test("[display] timeAgo()", () => {
   assertEquals(timeAgo(new Date(Date.now())), "just now");
   assertEquals(timeAgo(new Date(Date.now() - SECOND * 30)), "30 seconds ago");