implemented frontend including separate message system; started to implement backend

yjs-poll/node_modules/lib0/storage.js

@@ -0,0 +1,72 @@
+/* eslint-env browser */
+
+/**
+ * Isomorphic variable storage.
+ *
+ * Uses LocalStorage in the browser and falls back to in-memory storage.
+ *
+ * @module storage
+ */
+
+/* c8 ignore start */
+class VarStoragePolyfill {
+  constructor () {
+    this.map = new Map()
+  }
+
+  /**
+   * @param {string} key
+   * @param {any} newValue
+   */
+  setItem (key, newValue) {
+    this.map.set(key, newValue)
+  }
+
+  /**
+   * @param {string} key
+   */
+  getItem (key) {
+    return this.map.get(key)
+  }
+}
+/* c8 ignore stop */
+
+/**
+ * @type {any}
+ */
+let _localStorage = new VarStoragePolyfill()
+let usePolyfill = true
+
+/* c8 ignore start */
+try {
+  // if the same-origin rule is violated, accessing localStorage might thrown an error
+  if (typeof localStorage !== 'undefined' && localStorage) {
+    _localStorage = localStorage
+    usePolyfill = false
+  }
+} catch (e) { }
+/* c8 ignore stop */
+
+/**
+ * This is basically localStorage in browser, or a polyfill in nodejs
+ */
+/* c8 ignore next */
+export const varStorage = _localStorage
+
+/**
+ * A polyfill for `addEventListener('storage', event => {..})` that does nothing if the polyfill is being used.
+ *
+ * @param {function({ key: string, newValue: string, oldValue: string }): void} eventHandler
+ * @function
+ */
+/* c8 ignore next */
+export const onChange = eventHandler => usePolyfill || addEventListener('storage', /** @type {any} */ (eventHandler))
+
+/**
+ * A polyfill for `removeEventListener('storage', event => {..})` that does nothing if the polyfill is being used.
+ *
+ * @param {function({ key: string, newValue: string, oldValue: string }): void} eventHandler
+ * @function
+ */
+/* c8 ignore next */
+export const offChange = eventHandler => usePolyfill || removeEventListener('storage', /** @type {any} */ (eventHandler))