@reactivex/rxjs/compat/add/operator/startWith.ts

Reactive Extensions for modern JavaScript

import { Observable } from 'rxjs';
import { startWith } from '../../operator/startWith';

(Observable as any).prototype.startWith = startWith;

declare module 'rxjs/internal/Observable' {
  interface Observable<T> {
    startWith: typeof startWith;
  }
}