Convert punctuateSeries to TypeScript

framework/core/js/src/common/helpers/punctuateSeries.ts

@@ -0,0 +1,34 @@
+import type { Children } from 'mithril';
+import app from '../../common/app';
+
+/**
+ * Formats a list of strings/nodes to read fluently in the locale.
+ */
+export default function punctuateSeries(items: Children[] = []): Children {
+  if (items.length === 2) {
+    return app.translator.trans('core.lib.series.two_text', {
+      first: items[0],
+      second: items[1],
+    });
+  }
+
+  if (items.length >= 3) {
+    const glue = app.translator.trans('core.lib.series.glue_text') as Children;
+
+    // Build middle items safely: [item, glue, item, glue, ...]
+    const second: Children[] = [];
+    for (let i = 1; i < items.length - 1; i++) {
+      second.push(items[i]);
+      if (i < items.length - 2) second.push(glue);
+    }
+
+    return app.translator.trans('core.lib.series.three_text', {
+      first: items[0],
+      second,
+      third: items[items.length - 1],
+    });
+  }
+
+  // 0 or 1 item: return as-is (Mithril can render arrays too)
+  return items;
+}