Method on

src/tutorial/tutorialManager.js:137–142

* Register event listener * @param {string} event - Event name * @param {Function} callback - Callback function

(event, callback)

   * @param {Function} callback - Callback function
   */
  on(event, callback) {
    if (!this.listeners.has(event)) {
      this.listeners.set(event, []);
    }
    this.listeners.get(event).push(callback);
  }

  /**
   * Unregister event listener