title: Set Opacity with UI Slider on Leaflet _leaflet_id
body: <p>Using jquery UI, I have a slider setup passing in decimal numbers "0.1" to "0.9" in order to change the opacity of the current layer on the map.</p>
  
  <p>I am able to get the current layer ID, but cannot figure out how to change the opacity at this point.</p>
  
  <p>Using activeLayers plugin:</p>
  
  <pre><code>var overlayLayers = activeControl.getActiveOverlayLayers();
  </code></pre>
  
  <p>overlayLayers returns the current opacity correctly:</p>
  
  <pre><code>for (var overlayId in overlayLayers) {
      var lOpacity = overlayLayers[overlayId].layer.options.opacity;
      console.log(lOpacity);
  }
  </code></pre>
  
  <p>I have seen a few posts where folks are using setOpacity on the layer var, but not the layer ID. </p>
  
  <p>Can you not set opacity on layer id like:</p>
  
  <pre><code>lOpacity.setOpactiy(value);
  </code></pre>
  
  <p>or </p>
  
  <pre><code>overlayLayers[overlayId].layer.options.opacity="0.5";
  </code></pre>
  
  <p>What am I missing?</p>