docs: function List(editor) {
      this.editor = editor
      this.$elem = $('<div class="w-e-menu"><i class="w-e-icon-list2"></i></div>')
      this.type = 'droplist'
  
      // 当前是否 active 状态
      this._active = false
  
      // 初始化 droplist
      this.droplist = new DropList(this, {
          width: 120,
          $title: $('<p>设置列表</p>'),
          type: 'list', // droplist 以列表形式展示
          list: [
              { $elem: $('<span><i class="w-e-icon-list-numbered"></i> 有序列表</span>'), value: 'insertOrderedList' },
              { $elem: $('<span><i class="w-e-icon-list2"></i> 无序列表</span>'), value: 'insertUnorderedList' }
          ],
          onClick: (value) => {
              // 注意 this 是指向当前的 List 对象
              this._command(value)
          }
      })
  }