AJAX Simple

Hi,

I’m trying to work out the simplest way to reuse AJAX in a project.

This is what I have so far, would this work to reuse?

//AJAX Variables
var xhr = new XMLHttpRequest();
var _success = xhr.status == 200;
//AJAX Error Message
function no_msg(element){
                document.querySelector(element).innerHTML =
                "Oops. We have encountered an error.";                           
};
document.querySelector("#btn")
  .addEventListener('click', function(){
                              
                xhr;
                xhr.onload = function(){
                if(_success){
                h1.innerHTML = xhr.responseText;
                }
              
                else{
                no_msg("#text");
                }
              
                };
                xhr.open("GET", "data.txt", true);
                xhr.send();
});
console.log(xhr);

Code (JavaScript):

 

Learned the hard way that this is not possible...