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  1. import { mergeMap } from './mergeMap';
  2. import { identity } from '../util/identity';
  3. import { OperatorFunction, ObservableInput, ObservedValueOf } from '../types';
  4. /**
  5. * Converts a higher-order Observable into a first-order Observable which
  6. * concurrently delivers all values that are emitted on the inner Observables.
  7. *
  8. * <span class="informal">Flattens an Observable-of-Observables.</span>
  9. *
  10. * ![](mergeAll.png)
  11. *
  12. * `mergeAll` subscribes to an Observable that emits Observables, also known as
  13. * a higher-order Observable. Each time it observes one of these emitted inner
  14. * Observables, it subscribes to that and delivers all the values from the
  15. * inner Observable on the output Observable. The output Observable only
  16. * completes once all inner Observables have completed. Any error delivered by
  17. * a inner Observable will be immediately emitted on the output Observable.
  18. *
  19. * ## Examples
  20. *
  21. * Spawn a new interval Observable for each click event, and blend their outputs as one Observable
  22. *
  23. * ```ts
  24. * import { fromEvent, map, interval, mergeAll } from 'rxjs';
  25. *
  26. * const clicks = fromEvent(document, 'click');
  27. * const higherOrder = clicks.pipe(map(() => interval(1000)));
  28. * const firstOrder = higherOrder.pipe(mergeAll());
  29. *
  30. * firstOrder.subscribe(x => console.log(x));
  31. * ```
  32. *
  33. * Count from 0 to 9 every second for each click, but only allow 2 concurrent timers
  34. *
  35. * ```ts
  36. * import { fromEvent, map, interval, take, mergeAll } from 'rxjs';
  37. *
  38. * const clicks = fromEvent(document, 'click');
  39. * const higherOrder = clicks.pipe(
  40. * map(() => interval(1000).pipe(take(10)))
  41. * );
  42. * const firstOrder = higherOrder.pipe(mergeAll(2));
  43. *
  44. * firstOrder.subscribe(x => console.log(x));
  45. * ```
  46. *
  47. * @see {@link combineLatestAll}
  48. * @see {@link concatAll}
  49. * @see {@link exhaustAll}
  50. * @see {@link merge}
  51. * @see {@link mergeMap}
  52. * @see {@link mergeMapTo}
  53. * @see {@link mergeScan}
  54. * @see {@link switchAll}
  55. * @see {@link switchMap}
  56. * @see {@link zipAll}
  57. *
  58. * @param concurrent Maximum number of inner Observables being subscribed to
  59. * concurrently.
  60. * @return A function that returns an Observable that emits values coming from
  61. * all the inner Observables emitted by the source Observable.
  62. */
  63. export function mergeAll<O extends ObservableInput<any>>(concurrent: number = Infinity): OperatorFunction<O, ObservedValueOf<O>> {
  64. return mergeMap(identity, concurrent);
  65. }