diff --git a/src/lib/util.js b/src/lib/util.js
index 6b5c2a7..b885e21 100644
--- a/src/lib/util.js
+++ b/src/lib/util.js
@@ -29,3 +29,12 @@ export function gotoNamedId(id, name) {
   const page = getNamedId(id, name);
   goto(page, { replaceState: true });
 }
+
+/**
+ * @param {string | null | undefined} string 
+ * @returns {number | null}
+ */
+export function parseIntNull(string) {
+  const r = string ? parseInt(string) : null;
+  return Number.isNaN(r) ? null : r;
+}