docs: function FontSize(editor) {
      this.editor = editor
      this.$elem = $('<div class="w-e-menu"><i class="w-e-icon-text-heigh"></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: 160,
          $title: $('<p>字号</p>'),
          type: 'list', // droplist 以列表形式展示
          list: [
              { $elem: $('<span style="font-size: x-small;">x-small</span>'), value: '1' },
              { $elem: $('<span style="font-size: small;">small</span>'), value: '2' },
              { $elem: $('<span>normal</span>'), value: '3' },
              { $elem: $('<span style="font-size: large;">large</span>'), value: '4' },
              { $elem: $('<span style="font-size: x-large;">x-large</span>'), value: '5' },
              { $elem: $('<span style="font-size: xx-large;">xx-large</span>'), value: '6' }
          ],
          onClick: (value) => {
              // 注意 this 是指向当前的 FontSize 对象
              this._command(value)
          }
      })
  }