Suppose I have some code like this:-
const Ω = {};
Ω.getJSON = function(url, callback){
      var request = new XMLHttpRequest();
    request.open('GET', url, true);
    request.onload = function() {
      if (this.status >= 200 && this.status < 400) {
        var data = JSON.parse(this.response);
        callback(data);
      } else {
        console.log(this.status);
      }
    };
    request.onerror = function() {
      throw'An Unknown Error';
    };
    request.send();
    }
I want to define a .fail() function similar to jQuery's $.getJSON one but I have no idea how to do like this. 
How can I make a .fail() function for Ω.getJSON?
Answers and comments appreciated.
