docs: function Justify(editor) {
      this.editor = editor
      this.$elem = $('<div class="w-e-menu"><i class="w-e-icon-paragraph-left"></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: 100,
          $title: $('<p>对齐方式</p>'),
          type: 'list', // droplist 以列表形式展示
          list: [
              { $elem: $('<span><i class="w-e-icon-paragraph-left"></i> 靠左</span>'), value: 'justifyLeft' },
              { $elem: $('<span><i class="w-e-icon-paragraph-center"></i> 居中</span>'), value: 'justifyCenter' },
              { $elem: $('<span><i class="w-e-icon-paragraph-right"></i> 靠右</span>'), value: 'justifyRight' }
          ],
          onClick: (value) => {
              // 注意 this 是指向当前的 List 对象
              this._command(value)
          }
      })
  }