Reactive Programming with RxJS/

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Making Ajax Calls With an Observable

Making Ajax Calls With an Observable

Learn how to retrieve data through an HTTP request using Observers.

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We haven’t done anything useful with Observables yet. How about we create an Observable that retrieves remote content? To do this, we’ll wrap the XMLHttpRequest object using Rx.Observable.create:

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function get(url) 
{
  return Rx.Observable.create(function(observer) 
  {
    // Make a traditional Ajax request
    var req = new XMLHttpRequest(); req.open('GET', url);
    req.onload = function() 
    { 
      if (req.status == 200) 
      {
        // If the status is 200, meaning there have been no problems, // Yield the result to listeners and complete the sequence observer.onNext(req.response);
        observer.onCompleted();
      } 
      else 
      {
        // Otherwise, signal to listeners that there has been an error
        observer.onError(new Error(req.statusText)); 
      }
    };
  req.onerror = function() 
  {
    observer.onError(new Error("Unknown Error"));
  };
  req.send();
  });
}
// Create an Ajax Observable
var test = get('/api/contents.json');

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