implemented frontend including separate message system; started to implement backend

yjs-poll/node_modules/lib0/mutex.js

@@ -0,0 +1,43 @@
+/**
+ * Mutual exclude for JavaScript.
+ *
+ * @module mutex
+ */
+
+/**
+ * @callback mutex
+ * @param {function():void} cb Only executed when this mutex is not in the current stack
+ * @param {function():void} [elseCb] Executed when this mutex is in the current stack
+ */
+
+/**
+ * Creates a mutual exclude function with the following property:
+ *
+ * ```js
+ * const mutex = createMutex()
+ * mutex(() => {
+ *   // This function is immediately executed
+ *   mutex(() => {
+ *     // This function is not executed, as the mutex is already active.
+ *   })
+ * })
+ * ```
+ *
+ * @return {mutex} A mutual exclude function
+ * @public
+ */
+export const createMutex = () => {
+  let token = true
+  return (f, g) => {
+    if (token) {
+      token = false
+      try {
+        f()
+      } finally {
+        token = true
+      }
+    } else if (g !== undefined) {
+      g()
+    }
+  }
+}