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JavaScript

/**
* Module dependencies
*/
var XMLHttpRequest = require('xmlhttprequest-ssl');
var XHR = require('./polling-xhr');
var JSONP = require('./polling-jsonp');
var websocket = require('./websocket');
/**
* Export transports.
*/
exports.polling = polling;
exports.websocket = websocket;
/**
* Polling transport polymorphic constructor.
* Decides on xhr vs jsonp based on feature detection.
*
* @api private
*/
function polling (opts) {
var xhr;
var xd = false;
var xs = false;
var jsonp = false !== opts.jsonp;
if (typeof location !== 'undefined') {
var isSSL = 'https:' === location.protocol;
var port = location.port;
// some user agents have empty `location.port`
if (!port) {
port = isSSL ? 443 : 80;
}
xd = opts.hostname !== location.hostname || port !== opts.port;
xs = opts.secure !== isSSL;
}
opts.xdomain = xd;
opts.xscheme = xs;
xhr = new XMLHttpRequest(opts);
if ('open' in xhr && !opts.forceJSONP) {
return new XHR(opts);
} else {
if (!jsonp) throw new Error('JSONP disabled');
return new JSONP(opts);
}
}