catch failed page loads due to absent trailing slashes

...on instances with missing redirect rules

www/main.js

@@ -0,0 +1,28 @@
+define([
+    'jquery',
+], function ($) {
+/*  CryptPad's example NGINX config includes a list of pages
+    which should have their URLs rewritten to include a trailing slash.
+    Sometimes we create a new page and forget to add it to these list.
+    Sometimes people configure their instance without this rewrite rule.
+
+    In either case, they might enter a URL like `/checkup` (without the
+    trailing slash) and somehow end up trying to load this script. ¯\_(ツ)_/¯
+
+    This script helps to avoid reports of confusion due to blank pages
+    like in some of the comments here: (https://github.com/xwiki-labs/cryptpad/issues/246)
+    by using jquery to check if adding a trailing slash would help,
+    and redirecting automatically if so.
+*/
+    var pathname = window.location.pathname;
+    $.ajax({
+        url: `${pathname}/?cb=${+new Date()}`,
+        data: {},
+        complete: function (xhr) {
+            if (xhr.status !== 200) {
+                return void console.log("failure");
+            }
+            window.location = (pathname + '/');
+        },
+    });
+});