错误类型错误：无法读取未定义的属性（读取“valueOf”）

Question

我正在尝试迭代 JSON 数据并访问开始时间和结束时间的键。 在我的 API 代码中，我尝试了两种方法来做到这一点。 Console.log 未显示错误 但另一种循环方法在控制台中显示错误。

我的 show-api.ts 代码：-

import { Component, OnInit } from '@angular/core';
import {HttpClient} from '@angular/common/http';

interface Employee {
    Id: String;
    EmployeeName: String;
    StartTimeUtc: String;
    EndTimeUtc: String;
    EntryNotes: String;
    DeletedOn: String;
}


@Component({
selector: 'app-show-api',
templateUrl: './show-api.component.html',
styleUrls: ['./show-api.component.css']
})


export class ShowApiComponent implements OnInit {

li:any;
lis: any=[];


constructor(private http : HttpClient){
    
}

ngOnInit(): void {
    this.http.get('Api of my JSON file')
    .subscribe(Response => {

    
    if(Response){
        hideloader();
    }

    const employee: Employee[]=Response as Employee[];
    console.log(employee[1].EndTimeUtc.valueOf())//it is not showing error

    for(var i=0;i<1;i++)
    {

    const date1inString=(employee[i].EndTimeUtc.valueOf());//it is showing error
    
    
    const date2inString=(employee[i].StartTimeUtc.valueOf());//it is showing error
    

    console.log(date1inString);
    console.log(date2inString);

    }


    
    });
    function hideloader(){
    document.getElementById('loading')!.style.display = 'none';}
}}

控制台数据中显示以下错误

core.mjs:6485 ERROR TypeError: Cannot read properties of undefined (reading 'valueOf')
    at Object.next (show-api.component.ts:51:48)
    at ConsumerObserver.next (Subscriber.js:91:1)
    at SafeSubscriber._next (Subscriber.js:60:1)
    at SafeSubscriber.next (Subscriber.js:31:1)
    at map.js:7:1
    at OperatorSubscriber._next (OperatorSubscriber.js:13:1)
    at OperatorSubscriber.next (Subscriber.js:31:1)
    at filter.js:6:50
    at OperatorSubscriber._next (OperatorSubscriber.js:13:1)
    at OperatorSubscriber.next (Subscriber.js:31:1)

console.log 没有显示错误并正确显示日期，但是当我将其保存在变量中时，它在来自 API 的

[

{"Id": "aa",
"EmployeeName": "bb",
"StarTimeUtc": "cc",
"EndTimeUtc": "dd",
"EntryNotes": "ee",
"DeletedOn": null },

{"Id": "ff",
"EmployeeName": "gg",
"StarTimeUtc": "hh",
"EndTimeUtc": "ii",
"EntryNotes": "jj",
"DeletedOn": null },

]

Answer 1

API 的响应数据没有 StartTimeUtc。因此，您尝试读取未定义的 valueof() ，这会导致此错误。

这是一个拼写错误 StarTimeUtc 而不是 StartTimeUtc

Answer 2

检查你的 for 循环。我认为这个条件不对。

使用这个，并让我知道

for (let i = 0; i < employee.length; i++)