page_11.js

function get(url) {
  return Rx.Observable.create(function(observer) {
  
    var req = new XMLHttpRequest();
    req.open('GET', url);
    req.onLoad = function() {
      if (req.status == 200) {
        observer.onNext(req.response);  
        observer.onCompleted();  
      }
      else {
        observer.onError(new Error(req.statusTest));  
      }
    };
    req.onError = function() {
      observer.onError(Error("Unknown Error"));
    };
    
    req.send();
  
  });  
}

var test = get('https://www.wikipedia.org');

test.subscribe(
  function(x) { console.log('Result: ' + x); },
  function(err) { console.log('Error: ' + err); },
  function() { console.log('Completed'); }
);