如何使用按钮单击添加div部分并在视图上显示它

js file

  var i = 0;
      var original = document.getElementById('middle-section');
      document.getElementById('btn').onclick = duplicate();
      function duplicate() {
          var clone = original.cloneNode(true); // "deep" clone
          clone.id = "middle-section" + ++i;
          // or clone.id = ""; if the divs don't need an ID
          original.body.appendChild(clone);
      }js file

  var i = 0;
      var ori