title: what is the difference between angular.isUndefined(value) and not !(value)?
body: <p>I've tried:</p>
  
  <pre><code>if(angular.isUndefined(value)){
      // something
  }
  </code></pre>
  
  <p>and </p>
  
  <pre><code>if(!(value)){
      // something
  }
  </code></pre>
  
  <ul>
  <li>Is there a difference between the two?</li>
  <li>Is there a use-case to choose one instead of the other?</li>
  </ul>