Init. Map does not function and only working on backend at the moment.

node_modules/engine.io-client/lib/xmlhttprequest.js

@@ -0,0 +1,37 @@
+// browser shim for xmlhttprequest module
+
+var hasCORS = require('has-cors');
+
+module.exports = function (opts) {
+  var xdomain = opts.xdomain;
+
+  // scheme must be same when usign XDomainRequest
+  // http://blogs.msdn.com/b/ieinternals/archive/2010/05/13/xdomainrequest-restrictions-limitations-and-workarounds.aspx
+  var xscheme = opts.xscheme;
+
+  // XDomainRequest has a flow of not sending cookie, therefore it should be disabled as a default.
+  // https://github.com/Automattic/engine.io-client/pull/217
+  var enablesXDR = opts.enablesXDR;
+
+  // XMLHttpRequest can be disabled on IE
+  try {
+    if ('undefined' !== typeof XMLHttpRequest && (!xdomain || hasCORS)) {
+      return new XMLHttpRequest();
+    }
+  } catch (e) { }
+
+  // Use XDomainRequest for IE8 if enablesXDR is true
+  // because loading bar keeps flashing when using jsonp-polling
+  // https://github.com/yujiosaka/socke.io-ie8-loading-example
+  try {
+    if ('undefined' !== typeof XDomainRequest && !xscheme && enablesXDR) {
+      return new XDomainRequest();
+    }
+  } catch (e) { }
+
+  if (!xdomain) {
+    try {
+      return new global[['Active'].concat('Object').join('X')]('Microsoft.XMLHTTP');
+    } catch (e) { }
+  }
+};