title: Property 'catch' does not exist on type 'Observable<IEmployee[]>'
body: <p>I'm newbie for the angular. And current I'm learning angular 6 features.
  When I try to handle error there is some issues like,</p>
  
  <blockquote>
    <p>Module not found: Error: Can't resolve 'rxjs/add/observable/throw' in
    'D:\WORKSPACE\Angular5\binding\src\app'</p>
    
    <p>Module not found: Error: Can't resolve 'rxjs/add/operator/catch' in
    'D:\WORKSPACE\Angular5\binding\src\app'</p>
    
    <p>ERROR in src/app/employee.service.ts(20,14): error TS2339: Property
    'catch' does not exist on type 'Observable'</p>
  </blockquote>
  
  <p>Here is my employee.service.ts</p>
  
  <pre><code>import { Injectable } from '@angular/core';
  import { HttpClient, HttpErrorResponse } from '@angular/common/http';
  import { IEmployee } from './employee';
  import { Observable } from 'rxjs';
  import 'rxjs/add/operator/catch';
  import 'rxjs/add/observable/throw';
  
  //It self injectable defendency.
  @Injectable({
    providedIn: 'root'
  })
  export class EmployeeService {
  
    private _url: string = "/assets/data/employees.json";
  
    constructor(private http: HttpClient) { }
  
    getEmployees(): Observable&lt;IEmployee[]&gt;{
      return this.http.get&lt;IEmployee[]&gt;(this._url)
              .catch(this.errorHandler);                    
    }
  
    errorHandler(error: HttpErrorResponse){
        return Observable.throw(error.message || "Server Error");
    }
  }
  </code></pre>
  
  <p>employee.ts</p>
  
  <pre><code>export interface IEmployee{
      id : number,
      name : String,
      age : number
  }
  </code></pre>
  
  <p>I tried to solve this question using bellow link. But I couldn't get the answer for my question.</p>
  
  <p><a href="https://stackoverflow.com/questions/37073705/property-catch-does-not-exist-on-type-observableany">Property 'catch' does not exist on type 'Observable'</a>  and <a href="https://stackoverflow.com/questions/34515173/angular-http-get-with-typescript-error-http-get-map-is-not-a-function-in-n/34515276#34515276">Angular HTTP GET with TypeScript error http.get(…).map is not a function in [null]</a></p>
  
  <p>Please give me some solution. Thank you.</p>