title: How to remove previous layer when draw new?
body: <p>Current behaviour of Draw plugin is add every new drawing layer to the map:</p>
  
  <pre><code>map.on('draw:created', function (e) {
      var type = e.layerType,
          layer = e.layer;
  
      if (type === 'marker') {
          // Do marker specific actions
      }
  
      // Do whatever else you need to. (save to db, add to map etc)
      map.addLayer(layer);
  });
  </code></pre>
  
  <p>but how to improve this code to get it remove every previous layer when user draw new one? I can't understand how to call: <code>map.removeLayer(layer);</code> and say it that I want to remove previous, but not current layer.</p>