code: function sendHostname(appName, trackingId) {
      var url = 'https://www.google-analytics.com/collect';
      var hostname = location.hostname;
      var hitType = 'event';
      var eventCategory = 'use';
      var applicationKeyForStorage = 'TOAST UI ' + appName + ' for ' + hostname + ': Statistics';
      var date = window.localStorage.getItem(applicationKeyForStorage);
  
      // skip if the flag is defined and is set to false explicitly
      if (!type.isUndefined(window.tui) && window.tui.usageStatistics === false) {
          return;
      }
  
      // skip if not pass seven days old
      if (date && !isExpired(date)) {
          return;
      }
  
      window.localStorage.setItem(applicationKeyForStorage, new Date().getTime());
  
      setTimeout(function() {
          if (document.readyState === 'interactive' || document.readyState === 'complete') {
              imagePing(url, {
                  v: 1,
                  t: hitType,
                  tid: trackingId,
                  cid: hostname,
                  dp: hostname,
                  dh: appName,
                  el: appName,
                  ec: eventCategory
              });
          }
      }, 1000);
  }
docs: Send hostname on DOMContentLoaded.
  To prevent hostname set tui.usageStatistics to false.
  @param {string} appName - application name
  @param {string} trackingId - GA tracking ID
  @ignore