fix: monthly schedule label shows 21th/22th/31th (ordinal suffix for days >20) (#1577)

static/js/tasks.js

@@ -7,6 +7,7 @@ import markdownModule from './markdown.js';
 import * as spinnerModule from './spinner.js';
 import { makeWindowDraggable } from './windowDrag.js';
 import { sortModelIds } from './modelSort.js';
+import { ordinalSuffix } from './util/ordinal.js';
 
 const API_BASE = window.location.origin;
 let _open = false;
@@ -244,7 +245,7 @@ function _scheduleLabel(task) {
   }
   if (task.schedule === 'monthly') {
     const d = task.scheduled_day ?? 1;
-    const suffix = d === 1 ? 'st' : d === 2 ? 'nd' : d === 3 ? 'rd' : 'th';
+    const suffix = ordinalSuffix(d);
     return `Monthly on ${d}${suffix} at ${localTime}`;
   }
   return task.schedule || '—';

static/js/util/ordinal.js

@@ -0,0 +1,13 @@
+// Pure (browser-free) English ordinal suffix, e.g. 1 -> "st", 21 -> "st",
+// 22 -> "nd", 23 -> "rd", 11/12/13 -> "th". Extracted so it can be unit-tested.
+export function ordinalSuffix(n) {
+  const a = Math.abs(Math.trunc(Number(n) || 0));
+  const mod100 = a % 100;
+  if (mod100 >= 11 && mod100 <= 13) return 'th';
+  switch (a % 10) {
+    case 1: return 'st';
+    case 2: return 'nd';
+    case 3: return 'rd';
+    default: return 'th';
+  }
+}