Problem iterating through JSON in Angular

Question

In an Angular project I am working in I am trying to iterate through some JSON located in my project. The Angular project compiles but I keep getting the dreaded:

ERROR Error: Cannot find a differ supporting object '[object Object]' of type 'object'. NgFor only supports binding to Iterables such as Arrays.

As I understand it, you cannot iterate an Object of JSON (???) -- you have to somehow turn it into an Array or some "iterable" container/structure etc. in order to get the *ngFor to work. I have tried about everything on stack overflow -- I am missing the bit to change that object to an Array so the *ngFor in my newemployee.component.html works correctly:

<tr *ngFor="let employee of emplist">

This is my service typescript code (employee.service.ts):

import { Injectable } from '@angular/core';
import { Employee2 } from '../employee2';
import { HttpClient } from '@angular/common/http';
import { Observable, of } from 'rxjs';
import { catchError, map, tap } from 'rxjs/operators';
import { MessageService } from '../message.service';

@Injectable({
  providedIn: 'root',
})
export class EmployeeService {
  url: string;

  constructor(
    private http: HttpClient,
    private messageService: MessageService
  ) {
    this.url = `/assets/json/employees.json`;
  }

  //gets the Employees from the file:
  getEmployees(): Observable<Employee2[]> {
    return this.http //.get(this.url)
      .get<Employee2[]>(this.url)
      .pipe(catchError(this.handleError<Employee2[]>('getEmployees', [])));
  }

  private handleError<T>(operation = 'operation', result?: T) {
    return (error: any): Observable<T> => {
      console.error(error); // log to console instead

      this.log(`${operation} failed: ${error.message}`);

      // Let the app keep running by returning an empty result.
      return of(result as T);
    };
  }

  private log(message: string) {
    this.messageService.add(`EmployeeService: ${message}`);
  }
}

This is my newemployee.component.ts:

import { Component, OnInit } from '@angular/core';
import { Employee2 } from '../employee2';
import { EmployeeService } from '../services/employee.service';

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

export class NewemployeeComponent implements OnInit {
  emplist: Employee2[];

  // Inject the service into newemployees.component.ts file via a constructor.
  constructor(private employeeService: EmployeeService) {}
  ngOnInit(): void {

    this.employeeService.getEmployees().subscribe((data) => {
      this.emplist = data;
    });
  }
}

And this is newemployee.component.html:

<br>
<div class="col">

<h2>Department Store Employees</h2>
        <table class="table table-bordered table-striped">
          <thead class="thead-dark">
      <tr>
        <th scope="col">ID</th>
        <th scope="col">Name</th>
        <th scope="col">Salary</th>
        <th scope="col">Age</th>
      </tr>
  </thead>
  <tbody>
    <tr *ngFor="let employee of emplist">
        <td scope="row">{{employee.id}}</td>
        <td>{{employee.employee_name}} </td>
        <td>{{employee.employee_salary}}</td>
        <td>{{employee.employee_age}} </td>     
    </tr>
</tbody>
</table>
</div>

Also this is the interface for Employee2:

export interface Employee2{

    id: number;
    employee_name: string;
    employee_salary: number;
    employee_age: number;
    profile_image: string; //path to image.
}

Finally the JSON file employees:

{
    "status": "success",
    "data": [{
        "id": 1,
        "employee_name": "John Public",
        "employee_salary": 320800,
        "employee_age": 61,
        "profile_image": ""
    }, {
        "id": 2,
        "employee_name": "John Summers",
        "employee_salary": 170750,
        "employee_age": 63,
        "profile_image": ""
    }, {
        "id": 3,
        "employee_name": "James Cox",
        "employee_salary": 86000,
        "employee_age": 66,
        "profile_image": ""
    },{
        "id": 24,
        "employee_name": "Chuck Wilder",
        "employee_salary": 85600,
        "employee_age": 23,
        "profile_image": ""
    }],
    "message": "Successfully! All records has been fetched."
}

Ideally this is what it should look like

Answer 1

The JSON you're retrieving from the service doesn't return an array but an object, on your component you should do this:

this.employeeService.getEmployees().subscribe((data) => {
  this.emplist = data.data;
});

Since your service is returning an object, your *ngFor directive can't iterate through it.

Answer 2

Try with this changes. The problem is that You are converting the JSON to type which is not with the same structure.

extract interface Response {
    status: string;
    data: Employee2[];
}

getEmployees(): Observable<Response> {
    return this.http //.get(this.url)
      .get<Response>(this.url)
      .pipe(catchError(this.handleError<Response>('getEmployees', {})));
}

export class NewemployeeComponent implements OnInit {
  emplist: Employee2[];

  // Inject the service into newemployees.component.ts file via a constructor.
  constructor(private employeeService: EmployeeService) {}
  ngOnInit(): void {

    this.employeeService.getEmployees().subscribe((response) => {
      this.emplist = response.data;
    });
  }
}