code: function JSONPPolling (socket) {
      io.Transport['xhr-polling'].apply(this, arguments);
  
      this.index = io.j.length;
  
      var self = this;
  
      io.j.push(function (msg) {
        self._(msg);
      });
    }
docs: The JSONP transport creates an persistent connection by dynamically
  inserting a script tag in the page. This script tag will receive the
  information of the Socket.IO server. When new information is received
  it creates a new script tag for the new data stream.
  
  @constructor
  @extends {io.Transport.xhr-polling}
  @api public