diff --git a/framework/core/js/src/common/helpers/punctuateSeries.js b/framework/core/js/src/common/helpers/punctuateSeries.js
deleted file mode 100644
index ad8c70592d..0000000000
--- a/framework/core/js/src/common/helpers/punctuateSeries.js
+++ /dev/null
@@ -1,37 +0,0 @@
-import app from '../../common/app';
-
-/**
- * The `punctuateSeries` helper formats a list of strings (e.g. names) to read
- * fluently in the application's locale.
- *
- * ```js
- * punctuateSeries(['Toby', 'Franz', 'Dominion']) // Toby, Franz, and Dominion
- * ```
- *
- * @param {import('mithril').Children[]} items
- * @return {import('mithril').Children}')}
- */
-export default function punctuateSeries(items) {
-  if (items.length === 2) {
-    return app.translator.trans('core.lib.series.two_text', {
-      first: items[0],
-      second: items[1],
-    });
-  } else if (items.length >= 3) {
-    // If there are three or more items, we will join all but the first and
-    // last items with the equivalent of a comma, and then we will feed that
-    // into the translator along with the first and last item.
-    const second = items
-      .slice(1, items.length - 1)
-      .reduce((list, item) => list.concat([item, app.translator.trans('core.lib.series.glue_text')]), [])
-      .slice(0, -1);
-
-    return app.translator.trans('core.lib.series.three_text', {
-      first: items[0],
-      second,
-      third: items[items.length - 1],
-    });
-  }
-
-  return items;
-}
diff --git a/framework/core/js/src/common/helpers/punctuateSeries.ts b/framework/core/js/src/common/helpers/punctuateSeries.ts
new file mode 100644
index 0000000000..328d22e1ed
--- /dev/null
+++ b/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;
+}