How to throw an observable error manually?

Question

I am working on an Angular app in which I am making a rest call through HTTP as below:

login(email, password) {
    let headers = new Headers();
    headers.a         


        

Answer 1

with rxjs 6

import { throwError } from 'rxjs';
throwError('hello');

Answer 2

if (response.success == 0) {
   throw Observable.throw(response);  
 } 

Edit for rxjs 6:

if (response.success == 0) {
   throw throwError(response);  
 } 

Answer 3

rxjs 6

import { throwError } from 'rxjs';

if (response.success == 0) {
  return throwError(response);  
}

rxjs 5

import { ErrorObservable } from 'rxjs/observable/ErrorObservable';

if (response.success == 0) {
  return new ErrorObservable(response);  
}

What you return with ErrorObservable is up to you

Answer 4

Here is the official example (that emits number 7 and then error 'oops!'):

import { throwError, concat, of } from 'rxjs';

const result = concat(of(7), throwError(new Error('oops!')));
result.subscribe(x => console.log(x), e => console.error(e));

From: https://rxjs-dev.firebaseapp.com/api/index/function/throwError

Answer 5

Use the catch operator

this.calcSub = this.http.post(this.constants.userUrl + "UpdateCalculation", body, { headers: headers })
   .map((response: Response) => {
      var result = <DataResponseObject>response.json();
         return result;
   })
   .catch(this.handleError)
   .subscribe(
      dro => this.dro = dro,
      () => this.completeAddCalculation()
   );

And handle the error like this:

private handleError(error: Response) {
    console.error(error); // log to console instead
    return Observable.throw(error.json().error || 'Server Error');
}

Answer 6

Most of my issues were related to the imports, so here's the code that worked for me...

import {_throw} from 'rxjs/observable/throw';
login(email, password) {
...
    return this.http.post(`${this._configService.getBaseUrl()}/login`, body, options)
    .map((res: any) => {
...
        if (response.success == 0) {
           _throw(response);  
        } else if (response.success == 1) {
...
        }
    });
}

This will be the solution if you are facing errors like...

ERROR TypeError: WEBPACK_IMPORTED_MODULE_2_rxjs_Observable.Observable.throw is not a function