title: Modify the URL of a new Request Object in ES6
body: <p>I'm just playing around the with <code>Fetch</code> API and I came across something that I can't seem to find the answer to. If I create a new request object like so:</p>
  
  <pre><code>let request = new Request('http://www.foo.com', {
    method: 'GET',
    mode: 'no-cors',
    headers: new Headers({
  'Content-Type': 'application/x-www-form-urlencoded'
    })
  });
  </code></pre>
  
  <p>If I then try and modify the URL (append a query string to it) I receive an error in the browser (<code>Cannot assign to read only property</code>). I know that usually with an object, you can set <code>writable</code> to 'True' but does this work the same for a request object? </p>
  
  <p>The reason that I ask is that I am trying to append a querystring to the end of the URL. These <code>options</code> are in another object, which I've got the values of and concatenated into a string so that it's something like:</p>
  
  <p><code>number=1&amp;id=130&amp;foo=bar</code> etc.</p>
  
  <p>Am I trying to over engineer what I am doing here?</p>