右键菜单实现橡皮筋技术，点击右键，弹出菜单，然后选择要操作的内容。-Right menu achieve rubber band technology, right-click, pop-up menu, then select the contents of the operation.

buiw的橡皮筋特效代码，做主菜单类的同学肯定需要，上传了~-buiw viewport rubber banding