A sequence of items that arrive asynchronously over time. HTTP call - single item Single item - HTTP response

1. HTTP Get request from EmpService
2. Receive the observable and cast it into an employee array
3. Subscribe to the observable from EmpList and EmpDetail
4. Assign the employee array to a local variable

RxJS

• Reactive Extensions from Javascript
• External library to work with Obserables

employee.service.ts

import { Injectable } from '@angular/core';
import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { IEmployee } from './employee';
import { Observable } from 'rxjs';
import { catchError, retry } from 'rxjs/operators';
 
// @Injectable({
//   providedIn: 'root'
// })
@Injectable()
export class EmployeeService {
  private _url: string = "/assets/data/employees.json"
 
  constructor(private http: HttpClient) { }
 
  getEmployees(): Observable<IEmployee[]>{
    return this.http.get<IEmployee[]>(this._url)
      .pipe(
        catchError(this.errorHandler)
      );
  }
  errorHandler(error: HttpErrorResponse){
    return Observable.throw(error.message || "Server Error");
  }
}