我的 reactjs 组件 Alerts 按日期/名称对 json 数据进行排序，该组件可以正常工作，但单元测试无法正常工作，它在实用程序函数中中断了该测试，这就是问题所在。

Alertscomponent 的一部分使用了实用程序函数 createAlertsWithName 的一部分。它所做的就是将 2 个数组“合并”为 1 个（因为 alerts 数组不包含名称，而我需要它进行排序）：

export const createAlertsWithName = (alerts,applicants) =>{
    return alerts.map(a =>({
      ...a,
      name:(a.applicants
        .map(id =>getApplicantByid(id,applicants))
        .find(applicant => applicant.isPrimaryApplicant) ||{lastName:''}).lastName
    }))
  }

当我运行“npm test”时，出现以下错误消息：

Alerts › should render sorted data

    TypeError: Cannot read property 'isPrimaryApplicant' of undefined

       6 |       name:(a.applicants
       7 |         .map(id =>getApplicantByid(id,applicants))
    >  8 |         .find(applicant => applicant.isPrimaryApplicant) ||{lastName:''}).lastName
         |                                      ^
       9 |     }))
      10 |   }
      11 | 

      at isPrimaryApplicant (src/utility.js:8:38)
          at Array.find (<anonymous>)
      at find (src/utility.js:8:10)
          at Array.map (<anonymous>)
      at map (src/utility.js:4:19)
      at createAlertsWithName (src/utility.js:17:12)
      at Alerts.render (src/Alerts.js:12:11)

这似乎很奇怪，因为我检查了没有 find 语句的“name”属性，如下所示：

 name:(a.applicants
    .map(id =>getApplicantByid(id,applicants))

输出将是：

applicants: (2) ["000001262", "000001263"]
assignedDateTime: "2018-10-25T09:25:00Z"
createdDateTime: "2019-10-24T09:25:00Z"
dueDateTime: "2019-10-25T09:25:00Z"
id: "19d0da63-dfd0-4c00-a13a-cc822fc81297"
name: (2) [{…}, {…}]
subject: "What a nice day"
submissionId: "SUB200620150004197"
__proto__: Object
1:
applicants: ["000001201"]
assignedDateTime: "2018-10-25T09:25:00Z"
createdDateTime: "2018-10-24T09:25:00Z"
dueDateTime: "2018-10-25T09:25:00Z"
id: "19d0da63-dfd0-4c00-a13a-cc822fc81201"
name: [{…}]
subject: "Hello"
submissionId: "SUB200620150004201"

据我所知，它不会返回未定义的“name”。那么为什么我会收到“无法读取未定义的属性‘isPrimaryApplicant’”错误？