restructuring the project

src/utils/EventHandler.js

@@ -0,0 +1,70 @@
+/**
+ * @module utils
+ */
+
+/**
+ * General event handler implementation.
+ */
+export class EventHandler {
+  constructor () {
+    this.eventListeners = []
+  }
+
+  /**
+   * To prevent memory leaks, call this method when the eventListeners won't be
+   * used anymore.
+   */
+  destroy () {
+    this.eventListeners = null
+  }
+
+  /**
+   * Adds an event listener that is called when
+   * {@link EventHandler#callEventListeners} is called.
+   *
+   * @param {Function} f The event handler.
+   */
+  addEventListener (f) {
+    this.eventListeners.push(f)
+  }
+
+  /**
+   * Removes an event listener.
+   *
+   * @param {Function} f The event handler that was added with
+   *                     {@link EventHandler#addEventListener}
+   */
+  removeEventListener (f) {
+    this.eventListeners = this.eventListeners.filter(g => f !== g)
+  }
+
+  /**
+   * Removes all event listeners.
+   */
+  removeAllEventListeners () {
+    this.eventListeners = []
+  }
+
+  /**
+   * Call all event listeners that were added via
+   * {@link EventHandler#addEventListener}.
+   *
+   * @param {Transaction} transaction The transaction object
+   * @param {YEvent} event An event object that describes the change on a type.
+   */
+  callEventListeners (transaction, event) {
+    for (var i = 0; i < this.eventListeners.length; i++) {
+      try {
+        const f = this.eventListeners[i]
+        f(event, transaction)
+      } catch (e) {
+        /*
+          Your observer threw an error. This error was caught so that Yjs
+          can ensure data consistency! In order to debug this error you
+          have to check "Pause On Caught Exceptions" in developer tools.
+        */
+        console.error(e)
+      }
+    }
+  }
+}