event-target.js

module.exports = EventTarget;
var Class = require('./class');

/**
 * A browser-based event emitter that takes advantage of the built-in C++ eventing the browser provides, giving a
 * consistent eventing mechanism everywhere in your front-end app.
 */
function EventTarget() {
  Object.defineProperty(this, '__event_node', { value: document.createDocumentFragment() });
}


Class.extend(EventTarget, {
  // Add event listener
  addEventListener: function addEventListener(type, listener) {
    this.__event_node.addEventListener(type, listener);
  },

  on: function on(type, listener) {
    this.addEventListener(type, listener);
  },

  // Removes event listener
  removeEventListener: function removeEventListener(type, listener) {
    this.__event_node.removeEventListener(type, listener);
    if (listener && listener.__event_one) {
      this.__event_node.removeEventListener(type, listener.__event_one);
    }
  },

  off: function off(type, listener) {
    this.removeEventListener(type, listener);
  },

  // Add event listener to only get called once, returns wrapped method for removing if needed
  one: function one(type, listener) {
    if (typeof listener !== 'function') return;

    if (!listener.__event_one) {
      var self = this;
      Object.defineProperty(listener, '__event_one', { value: function(event) {
        self.removeEventListener(type, listener.__event_one);
        listener.call(self, event);
      }});
    }

    this.addEventListener(type, listener.__event_one);
  },

  // Dispatch event and trigger listeners
  dispatchEvent: function dispatchEvent(event) {
    Object.defineProperty(event, 'target', { value: this });
    return this.__event_node.dispatchEvent(event);
  }
});