add saving draft to localStorage

data/static/js/bits/progressive-enhancement.js

@@ -3,6 +3,10 @@ export const b = {
 }
 
 export function enhance(_, __, el) {
+  if (el === undefined) { // nothing to enhance but init still runs
+    return;
+  }
+
   if (el.classList.contains('js-only')) {
     el.classList.remove('js-only');
   }

data/static/js/bits/ui.js

@@ -3,6 +3,14 @@ export const b = {
   init: 'babycodeEditorCharCountInit',
 }
 
+const getThreadId = () => {
+  const scheme = window.location.pathname.split("/");
+  if (scheme[1] !== 'threads' || scheme[2] === 'new') {
+    return -1;
+  }
+  return parseInt(scheme[2]);
+}
+
 export function setTab(_, sender, el) {
   if (sender.ariaSelected === 'true') {
     return;
@@ -95,10 +103,24 @@ export function babycodeEditorCharCount(evOrPayload, sender, el) {
   const maxLength = sender.maxLength;
   const currentLength = sender.value.length;
 
-  el.innerText = `${currentLength}/${maxLength}`
+  el.innerText = `${currentLength}/${maxLength}`;
+
+  const threadId = getThreadId();
+
+  if (threadId !== -1) {
+    localStorage.setItem(`thread-${threadId}`, sender.value);
+  }
 }
 
 export function babycodeEditorCharCountInit(_, __, el) {
+  if (el === undefined) { // no editors on page
+    return;
+  }
+
+  const threadId = getThreadId();
+  if (threadId !== -1) {
+    el.value = localStorage.getItem(`thread-${threadId}`);
+  }
   b.send({ sender: el }, 'babycodeEditorCharCount');
 }