code: function initButtonEvent () {
  
          $( "#penBtn" ).on( "click", function () {
  
              controller.enableDraw();
              controller.disableModify();
  
          } );
  
  
          $( "#modifyBtn" ).on( "click", function () {
  
              controller.disableDraw();
              controller.enableModify();
  
          } );
  
      }
docs: 启动按钮的控制事件