Make ajax requeste with no library

ajaxxhr.js

var success = function(){
  console.log(this.responseText);
  if(typeof callback === 'function')
     callback();				
};
var error = function(){
  console.log('=>error');
};			
var xhr = new XMLHttpRequest();
xhr.open("GET", "http://ksapirest.herokuapp.com/v1/sessiontvs/43037", true); 
xhr.send();
xhr.onload = success;	    	
xhr.onerror = error;