Work on login screen

src/lib/util.ts

@@ -0,0 +1,31 @@
+import {throttle} from 'throttle-debounce'
+import {browser} from '$app/environment'
+import {writable} from 'svelte/store'
+
+export const parseJson = (json: string) => {
+  if (!json) return null
+
+  try {
+    return JSON.parse(json)
+  } catch (e) {
+    return null
+  }
+}
+
+export const getJson = (k: string) =>
+  browser ? parseJson(localStorage.getItem(k) || "") : null
+
+export const setJson = (k: string, v: any) => {
+  if (browser) {
+    localStorage.setItem(k, JSON.stringify(v))
+  }
+}
+
+export const synced = <T>(key: string, defaultValue: T, delay = 300) => {
+  const init = getJson(key)
+  const store = writable<T>(init === null ? defaultValue : init)
+
+  store.subscribe(throttle(delay, (value: T) => setJson(key, value)))
+
+  return store
+}