title: Cannot delete object property in Javascript
body: <pre><code>obj = {a: []}
  </code></pre>
  
  <p>I want to delete <code>obj.a</code>. This code works    </p>
  
  <pre><code>if(!obj.a.length)
      delete obj.a //work
  </code></pre>
  
  <p>This is not  </p>
  
  <pre><code>function _delete(o) {
      if(!o.length)
        delete o 
  }
  
  _delete(obj.a) //not work
  </code></pre>
  
  <p>Any way to make it works?</p>