title: "rxjs" observable.throw is not a function - Angular4
body: <p>I've been learning Angular 4 and everything was going smoothly until I tried to implement catch handling in a service. I'm trying to use "rxjs" catch and throw but I've got an undefined function error in my console. </p>
  
  <pre class="lang-js prettyprint-override"><code>import { Injectable } from '@angular/core';
  import { Http } from "@angular/http";
  import { Observable } from 'rxjs/observable';
  import 'rxjs/add/operator/catch';
  import 'rxjs/add/observable/throw';
  import { AppError } from "../app/common/app.error";
  import { NotFoundError } from "../app/common/not-found-error";
  import { BadInput } from "../app/common/bad-input";
  
  @Injectable()
  export class PostService {
    private url = "https://jsonplaceholder.typicode.com/posts";
  
    constructor(private http: Http) { }
  
   deletepost(post){
        // return this.http.delete(this.url + '/' + post.id)
        // Hard-coded id to test 404
        return this.http.delete(this.url + '/' + 93498)
          .catch((error: Response) =&gt; {
            console.log('error within catch is ' + Response)
            if(error.status === 404)
              return Observable.throw(new NotFoundError(error));
  
            return Observable.throw(new AppError(error));
          });
      }
  }
  </code></pre>
  
  <p>This is the error message:</p>
  
  <pre><code>TypeError: __WEBPACK_IMPORTED_MODULE_2_rxjs_observable__["Observable"].throw is not a function. 
  (In '__WEBPACK_IMPORTED_MODULE_2_rxjs_observable__["Observable"].throw(new 
  __WEBPACK_IMPORTED_MODULE_6__app_common_not_found_error__["a" /* NotFoundError 
  */](error))', 
  '__WEBPACK_IMPORTED_MODULE_2_rxjs_observable__["Observable"].throw' is 
  undefined) — post.service.ts:42
  </code></pre>
  
  <p>I also have this warning in my browser:</p>
  
  <pre><code>./~/rxjs/Observable.js
  There are multiple modules with names that only differ in casing.
  This can lead to unexpected behavior when compiling on a filesystem with other case-semantic.
  Use equal casing. Compare these module identifiers:
  * /Users/nickgowdy/Desktop/Angular2/angular4 source code/hello-world/node_modules/rxjs/Observable.js
      Used by 14 module(s), i. e.
      /Users/nickgowdy/Desktop/Angular2/angular4 source code/hello-world/node_modules/@angular/core/@angular/core.es5.js
  * /Users/nickgowdy/Desktop/Angular2/angular4 source code/hello-world/node_modules/rxjs/observable.js
      Used by 1 module(s), i. e.
      /Users/nickgowdy/Desktop/Angular2/angular4 source code/hello-world/node_modules/@ngtools/webpack/src/index.js!/Users/nickgowdy/Desktop/Angular2/angular4 source code/hello-world/src/services/post.service.ts
  </code></pre>