title: how to remove all <div> elements inside a parent <div> in Shiny
body: <p>I'm hoping I don't need to provide a repro demo here if this question can be answered right away. I'd like to remove all <code>div</code> elements under the parent <code>div with id="daterangescontrol"</code> everytime I upload a file to my Shiny app. So my code is like this: </p>
  
  <pre><code>removeUI(selector = "div#daterangescontrol div")
  </code></pre>
  
  <p>FYI under <code>div#daterangescontrol</code>, there are <code>div#daterange1</code>, <code>div#daterange2</code>...<code>div#daterange(n)</code> generated dynamically depending on the number of columns in the dataset, which can be converted to Date. My objective is to remove all these div children when a new file is uploaded (new dataset). However. the above line of code can only remove the first child, e.g. <code>div#daterange1</code>. I wonder whether it's because I didn't use the right syntax for the selector. I'm not quite familiar with css. Would anyone please help? Thanks!</p>
  
  <p><strong>EDIT:</strong> 
  The demo code is provided in my other question post: 
  <a href="https://stackoverflow.com/questions/44600848/how-to-validate-date-range-input-in-shiny">How to validate date range input in Shiny</a>
  please check <code>removeUI</code> in <code>observeEvent(input$file)</code>. </p>