开玩笑+酶，使用mount（），document.getElementById（）在_method调用后出现的组件上返回null

通过hung和Google之神找到了解决方案：

1. 通过

   attachTo

   param将我的组件附加到DOM ：

        const result = mount(        <App />, { attachTo: document.body }    );

1. 将我的方法中的越野车字符串更改为与元素Object一起使用的字符串

    agentToMod.location = locationSelect.options[locationSelect.selectedIndex].text;` :     _modifyAgentStatus () {        const { currentAgentProfile, agentsDatabase } = this.state;        const agentToMod = currentAgentProfile;        if (agentToMod.status === 'Free') { this.setState({     infoDisplayContent: 'mission' }); agentToMod.status = 'Waiting';        } else if (agentToMod.status === 'Waiting') { const locationSelect = document.getElementById('missionLocationSelect'); agentToMod.location = agentToMod.location = locationSelect.options[locationSelect.selectedIndex].text; agentToMod.status = 'On Mission'; this.setState({     infoDisplayContent: 'profile'     }); }        }