Droppable

<!DOCTYPE html>
<html lang="ja">
  <head>
    <meta charset="utf-8">
    <title>jQuery UI</title>
    <link rel="stylesheet" href="jquery-ui.min.css">
    <script src="./external/jquery/jquery.js"></script>
    <script src="jquery-ui.min.js"></script>
    <style>
    .box {
    width: 50px;
    height: 50px;
    background: #ccc;
    margin-bottom: 20px;
    }
    .target {
      width: 100px;
      height: 100px;
      background: pink;
    }
  </style>
  </head>
  <body>
  <div class="box">box</div>
  <div class="target">target</div>
  <script>
    $(function(){
      $('.box').draggable();
      $('.target').droppable({
        accept: '.box',
        drop: function(event, ui){
          console.log('dropped!');
        }
      });
      });
  </script>
  </body>
</html>

ui追加

    $(function(){
      $('.box').draggable({
        helper: 'clone'
      });
      $('.target').droppable({
        accept: '.box',
        hoverClass: 'hover',
        tolerance: 'fit',
        drop: function(event, ui){
          ui.draggable.clone().appendTo(this);
          console.log('dropped!');
        }
      });
      });