1
 2/**
 3 * Module dependencies.
 4 */
 5
 6var XHR = require('./polling-xhr');
 7var JSONP = require('./polling-jsonp');
 8
 9/**
10 * Export transports.
11 */
12
13module.exports = exports = {
14  polling: polling,
15  websocket: require('./websocket')
16};
17
18/**
19 * Export upgrades map.
20 */
21
22exports.polling.upgradesTo = ['websocket'];
23
24/**
25 * Polling polimorphic constructor.
26 *
27 * @api private
28 */
29
30function polling (req) {
31  if ('string' == typeof req._query.j) {
32    return new JSONP(req);
33  } else {
34    return new XHR(req);
35  }
36}