title: How to modify data in Observable in Angular 2?
body: <p>I am working on learning Angular 2 and Typescript. I am building a simple web application that grabs data from a WEB API and displays it in a list. Then once the user clicks an item in the list, they are taken to a details page. </p>
  
  <p>I have a service that I created to make the API call that does the following: </p>
  
  <pre><code>   GetData() { 
           let data = this.http.get('http://server.name/api/GetData')
                    .map((res) =&gt; res.json());
           return data; 
     }
  </code></pre>
  
  <p>Then in a component, I subscribe to the data like this: </p>
  
  <pre><code>      this.myService.GetData()
        .subscribe((myService) =&gt; this.items = myService);
  </code></pre>
  
  <p>When the http.get returns, I would like to do some processing on the JSON objects before I return from the GetData() method. For example, add a new property called ID. Essentially something like the pseudo code below:</p>
  
  <pre><code> for each(item in data) { 
       item.ID = newID(); //method for creating IDs 
   }
  </code></pre>
  
  <ol>
  <li>Is this something that can be done?</li>
  <li>If yes, is it something that SHOULD be done, or is there a better way to accomplish what I am trying to do? </li>
  </ol>
  
  <p>Thanks </p>