resource-watcher-0.1.0.js

'use strict';
const resourceWatcher = function (url, conf) {
  let token = function (conf) {
    return conf && (conf = conf.Authorization) &&
      (conf = typeof conf === 'string' &&
        conf.split('=')) &&
      Array.isArray(conf) && conf[1];
  };

  url += '?token=' + token(conf);
  url += conf.timeout ? '&timeout=' + conf.timeout : '';
  let es = new EventSource(url); //jshint ignore: line
  let close = function () {
    es.close();
  };

  const makeHandler = function (handler, close) {
    return function (e) {
      if (close) {
        close();
      }

      return handler(e.data ? JSON.parse(e.data) : e);
    };
  };

  const on = function (event, handler) {
    switch (event) {
      case 'connect':
        es.onopen = makeHandler(handler);
        break;
      case 'change':
        es.onmessage = makeHandler(handler);
        break;
      case 'error':
        es.onerror = makeHandler(handler, close);
        break;
      default:
        console.error('Unknown event type:' + event);
        break;
    }
  };

  return {
    close: close,
    on: on,
  };
};