Promise listener for an event that will resolve when event fired

EventDeferred.js

import SymbolImpl from 'SymbolImpl';

const INTERNALS_FIELD = SymbolImpl('event.deferred::internals');

class EventDeferred {
  constructor(dispatcher, eventType) {
    this.promise = new Promise((resolve, reject) => {
      this[INTERNALS_FIELD] = {
        dispatcher,
        eventType,
        resolve,
        reject,
        handler: (event) => {
          const { resolve } = this[INTERNALS_FIELD];
          this.cancel();
          resolve(event);
        },
      };
    });
    dispatcher.addEventListener(eventType, this[INTERNALS_FIELD].handler);
  }

  get dispatcher() {
    return this[INTERNALS_FIELD].dispatcher;
  }

  get eventType() {
    return this[INTERNALS_FIELD].eventType;
  }

  get listening() {
    return !this[INTERNALS_FIELD].resolve;
  }

  cancel = () => {
    const { dispatcher, eventType, handler } = this[INTERNALS_FIELD];
    dispatcher.removeEventListener(eventType, handler);
    delete this[INTERNALS_FIELD].resolve;
  };

  reject = (data = null) => {
    const { reject } = this[INTERNALS_FIELD];
    this.cancel();
    reject(data);
  };

  dispose = () => {
    delete this[INTERNALS_FIELD];
  };
}

export default EventDeferred;

package.json

{
  "name": "EventDeferred",
  "description": "Promise listener for an event that will resolve when event fired",
  "version": "0.0.1",
  "main": "EventDeferred.js",
  "dependencies": {
    "SymbolImpl": "https://gist.github.com/burdiuz/7664491eed84695250e46be20670be84"
  }
}