react-router-ga/example/node_modules/sockjs-client/lib/transport/xhr-polling.js

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'use strict';

var inherits = require('inherits')
  , AjaxBasedTransport = require('./lib/ajax-based')
  , XhrReceiver = require('./receiver/xhr')
  , XHRCorsObject = require('./sender/xhr-cors')
  , XHRLocalObject = require('./sender/xhr-local')
  ;

function XhrPollingTransport(transUrl) {
  if (!XHRLocalObject.enabled && !XHRCorsObject.enabled) {
    throw new Error('Transport created when disabled');
  }
  AjaxBasedTransport.call(this, transUrl, '/xhr', XhrReceiver, XHRCorsObject);
}

inherits(XhrPollingTransport, AjaxBasedTransport);

XhrPollingTransport.enabled = function(info) {
  if (info.nullOrigin) {
    return false;
  }

  if (XHRLocalObject.enabled && info.sameOrigin) {
    return true;
  }
  return XHRCorsObject.enabled;
};

XhrPollingTransport.transportName = 'xhr-polling';
XhrPollingTransport.roundTrips = 2; // preflight, ajax

module.exports = XhrPollingTransport;