code: function Salesforce(username, password, token, wsdl) {
  
      //Required NodeJS libraries
      this.q = require("q");
      this.soap = require("soap");
  
      //Salesforce access data
      this.username = username;
      this.password = password;
      this.token = token;
      this.wsdl = wsdl || "./node_modules/soap_salesforce/wsdl/enterprise.xml";
  
      //Other properties
      this.promise; //A promise will be used for returning soapClient after finishing Salesforce login
      this.soapClient; //Salesforce SOAP client instance will be stored here
  }
docs: Salesforce connection library constructor.