Javascript 如何选择<；李>；在reactjs的按钮范围中，下拉列表

没用。如何处理此代码？也许使用TabCydiy＝'1，2,3/P>>P>使用OnFooCube（）事件，并考虑将TabEngy提供给LI本身。此外，使按钮的测试依赖于状态变量，该变量是在选项之间切换时设置的。下面是一个工作示例

userevent =(event)=>{

  console.log(event)
}

{this.state.selected}

{this.setState（{selected:e.target.value}}}>1.select

{this.setState（{selected:e.target.value}}}>{console.log（e.target.parentElement.value）}>2.select

{this.setState（{selected:e.target.value}}}>3.select

{this.setState（{selected:e.target.value}}}>4.select

这些是我所做的更改：
1.将Tabindex从a移动到li。
2.将按钮中的文本替换为此.state.selected
3.向每个li添加了onFocus事件处理程序

您可以进一步重构它。不要忘记在构造函数中设置初始状态

userevent =(event)=>{

  console.log(event)
}

<div className="input-group-btn" data-dropdown>

                            <button className="btn btn-default dropdown-toggle" type="button"
                                    data-toggle="dropdown" aria-expanded="true">
                                <span id="sortevent1" tabindex="0">{this.state.selected}</span><span
                                id="arrow" className="glyphicon glyphicon-align-center"></span>

                            </button>
                            <ul className="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1">
                                <li role="presentation"  tabindex="1" onFocus={(e)=>{this.setState({selected:e.target.value})}}><a role="menuitem"  >1.select &nbsp;<span id="arrow-up"
                                                            className="glyphicon glyphicon-indent-right"></span></a>
                                </li>
                                <li role="presentation"  tabindex="2" onFocus={(e)=>{this.setState({selected:e.target.value})}}><a role="menuitem"   onFocus={(e)=>{console.log(e.target.parentElement.value)}}>2.select &nbsp;<span id="arrow-down"
                                                            className="glyphicon glyphicon-indent-left"></span></a>
                                </li>
                                <li role="presentation" tabindex="3" onFocus={(e)=>{this.setState({selected:e.target.value})}}><a role="menuitem" >3.select&nbsp;<span id="arrow-up"
                                                            className="glyphicon glyphicon-indent-right"></span></a>
                                </li>

                                <li role="presentation" tabindex="4"  onFocus={(e)=>{this.setState({selected:e.target.value})}}><a role="menuitem" >4.select&nbsp;<span id="arrow-up"
                                                         className="glyphicon glyphicon-indent-right"></span></a>
                                </li>

                            </ul>

            </div>