title: How to use the .openPopup method in a feature group?
body: <p>I have a set of markers that have binded popups, but I can't figure out how to show all the popups when the marker group is toggled in the layers control. </p>
  
  <blockquote>
    <p>For example, I have my markers like so:</p>
  </blockquote>
  
  <pre><code>var testMarker = L.marker([32.9076,33.35449]).bindPopup('Marker 1');
  var testMarkerTwo = L.marker([33.58259,34.64539]).bindPopup('Marker 2');
  </code></pre>
  
  <blockquote>
    <p>Then, I put it in a freature group and append the <code>openPopup</code> method:</p>
  </blockquote>
  
  <pre><code>var markerGroup = L.featureGroup([testMarker,testMarkerTwo]).openPopup().addTo(map);
  </code></pre>
  
  <p>This doesn't work. </p>
  
  <p>My final goal is to add that featureGroup to my layers control where I can toggle the group off/on. Before I get to that part, I need to first understand why the openPopup method is not working. </p>
  
  <p><strong>Edit: The answer below appears to only work with the plain Leaflet API, not the Mapbox API.</strong></p>