EventDispatcher.js

'use strict';

/**
 * By Pipo From three.js, in turn form https://github.com/mrdoob/eventdispatcher.js/
 */

class EventDispatcher {
  addEventListener(type, listener) {
    if (this._listeners === undefined) this._listeners = {};
    const listeners = this._listeners;
    if (listeners[type] === undefined) {
      listeners[type] = [];
    }
    if (listeners[type].indexOf(listener) === -1) {
      listeners[type].push(listener);
    }
  }

  hasEventListener(type, listener) {
    if (this._listeners === undefined) return false;
    const listeners = this._listeners;
    return listeners[type] !== undefined &&
      listeners[type].indexOf(listener) !== -1;
  }

  removeEventListener(type, listener) {
    if (this._listeners === undefined) return;
    const listeners = this._listeners;
    const listenerArray = listeners[type];
    if (listenerArray !== undefined) {
      const index = listenerArray.indexOf(listener);
      if (index !== -1) {
        listenerArray.splice(index, 1);
      }
    }
  }

  dispatchEvent(event) {
    if (this._listeners === undefined) return;
    const listeners = this._listeners;
    const listenerArray = listeners[event.type];
    if (listenerArray !== undefined) {
      event.target = this;

      // Make a copy, in case listeners are removed while iterating.
      const array = listenerArray.slice(0);
      for (let i = 0, l = array.length; i < l; i++) {
        array[i].call(this, event);
      }
      event.target = null;
    }
  }

}