title: How do I validate favicons using Javascript?
body: <p>In a previous post on <a href="https://stackoverflow.com/questions/7034333/adding-favicons-with-generic-option">SO</a> I asked how to display favicons with a generic option for favicons that do not exist.  </p>
  
  <pre><code>&lt;img src="example.com/favicon.ico"; alt=""/&gt;
  </code></pre>
  
  <p>This code was posted:</p>
  
  <pre><code>var img = document.getElementsByTagName('img')[0],
      favicon = new Image;
  
  favicon.src = 'http://example.com/favicon.ico'
  
  favicon.onerror = function() 
    {
    img.src = 'http://url-on-local-server.com/favicon.ico';
    }
  </code></pre>
  
  <p>However I do not understand the need for "new Image", why can't I just use the existing image like this?</p>
  
  <pre><code>var img = document.getElementsByTagName('img')[0],
  img.src = 'http://example.com/favicon.ico'
  img.onerror = function() 
    {
    img.src = 'http://url-on-local-server.com/favicon.ico';
    }
  </code></pre>