diff --git a/js/prefs.js b/js/prefs.js
deleted file mode 100644
index 7c338ef..0000000
--- a/js/prefs.js
+++ /dev/null
@@ -1,30 +0,0 @@
-/* Copyright 2010-2019 Will Scullin <scullin@scullinsteel.com>
- *
- * Permission to use, copy, modify, distribute, and sell this software and its
- * documentation for any purpose is hereby granted without fee, provided that
- * the above copyright notice appear in all copies and that both that
- * copyright notice and this permission notice appear in supporting
- * documentation.  No representations are made about the suitability of this
- * software for any purpose.  It is provided "as is" without express or
- * implied warranty.
- */
-
-/*exported Prefs */
-
-export default function Prefs()
-{
-    return {
-        havePrefs: function() {
-            return typeof(localStorage) !== 'undefined';
-        },
-        readPref: function(name) {
-            if (localStorage)
-                return localStorage.getItem(name);
-            return null;
-        },
-        writePref: function(name, value) {
-            if (localStorage)
-                localStorage.setItem(name, value);
-        }
-    };
-}
diff --git a/js/prefs.ts b/js/prefs.ts
new file mode 100644
index 0000000..b17601a
--- /dev/null
+++ b/js/prefs.ts
@@ -0,0 +1,23 @@
+/* Copyright 2010-2023 Will Scullin <scullin@scullinsteel.com>
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that
+ * copyright notice and this permission notice appear in supporting
+ * documentation.  No representations are made about the suitability of this
+ * software for any purpose.  It is provided "as is" without express or
+ * implied warranty.
+ */
+
+export default class Prefs {
+  havePrefs() {
+    return typeof localStorage !== "undefined";
+  }
+  readPref(name: string) {
+    if (localStorage) return localStorage.getItem(name);
+    return null;
+  }
+  writePref(name: string, value: string) {
+    if (localStorage) localStorage.setItem(name, value);
+  }
+}