handle forbidden and not found errors on text page

public/js/text.js

@@ -4,8 +4,24 @@ document.addEventListener('DOMContentLoaded', () => {
     const textId = window.location.pathname.split('/').pop();
 
     fetch('/api/texts/' + textId, { credentials: 'same-origin' })
-        .then(res => res.json())
+        .then(function (res) {
-        .then(text => {
+            if (!res.ok) {
+                if (res.status === 403) {
+                    const message = document.createElement('p');
+                    message.textContent =
+                        "You don't have permission to view this text";
+                    document.getElementById('text-detail').appendChild(message);
+                } else if (res.status === 404) {
+                    const message = document.createElement('p');
+                    message.textContent = 'Text not found';
+                    document.getElementById('text-detail').appendChild(message);
+                }
+                return;
+            }
+            return res.json();
+        })
+        .then(function (text) {
+            if (!text) return;
             const h1 = document.createElement('h1');
             h1.textContent = text.name;
             document.getElementById('text-detail').appendChild(h1);