@firefox-devtools/react-contextmenu/es6/globalEventListener.js

Context Menu implemented in React

import { MENU_SHOW, MENU_HIDE } from './actions';
import { uniqueId, hasOwnProp, canUseDOM } from './helpers';
class GlobalEventListener {
  constructor() {
    this.callbacks = {};
    if (canUseDOM) {
      window.addEventListener(MENU_SHOW, this.handleShowEvent);
      window.addEventListener(MENU_HIDE, this.handleHideEvent);
    }
  }
  handleShowEvent = event => {
    for (const id in this.callbacks) {
      if (hasOwnProp(this.callbacks, id)) this.callbacks[id].show(event);
    }
  };
  handleHideEvent = event => {
    for (const id in this.callbacks) {
      if (hasOwnProp(this.callbacks, id)) this.callbacks[id].hide(event);
    }
  };
  register = (showCallback, hideCallback) => {
    const id = uniqueId();
    this.callbacks[id] = {
      show: showCallback,
      hide: hideCallback
    };
    return id;
  };
  unregister = id => {
    if (id && this.callbacks[id]) {
      delete this.callbacks[id];
    }
  };
}
export default new GlobalEventListener();