partition.d.ts 2.3 KB

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  1. import { ObservableInput } from '../types';
  2. import { Observable } from '../Observable';
  3. /**
  4. * Splits the source Observable into two, one with values that satisfy a
  5. * predicate, and another with values that don't satisfy the predicate.
  6. *
  7. * <span class="informal">It's like {@link filter}, but returns two Observables:
  8. * one like the output of {@link filter}, and the other with values that did not
  9. * pass the condition.</span>
  10. *
  11. * ![](partition.png)
  12. *
  13. * `partition` outputs an array with two Observables that partition the values
  14. * from the source Observable through the given `predicate` function. The first
  15. * Observable in that array emits source values for which the predicate argument
  16. * returns true. The second Observable emits source values for which the
  17. * predicate returns false. The first behaves like {@link filter} and the second
  18. * behaves like {@link filter} with the predicate negated.
  19. *
  20. * ## Example
  21. * Partition a set of numbers into odds and evens observables
  22. * ```ts
  23. * import { of, partition } from 'rxjs';
  24. *
  25. * const observableValues = of(1, 2, 3, 4, 5, 6);
  26. * const [evens$, odds$] = partition(observableValues, (value, index) => value % 2 === 0);
  27. *
  28. * odds$.subscribe(x => console.log('odds', x));
  29. * evens$.subscribe(x => console.log('evens', x));
  30. *
  31. * // Logs:
  32. * // odds 1
  33. * // odds 3
  34. * // odds 5
  35. * // evens 2
  36. * // evens 4
  37. * // evens 6
  38. * ```
  39. *
  40. * @see {@link filter}
  41. *
  42. * @param {function(value: T, index: number): boolean} predicate A function that
  43. * evaluates each value emitted by the source Observable. If it returns `true`,
  44. * the value is emitted on the first Observable in the returned array, if
  45. * `false` the value is emitted on the second Observable in the array. The
  46. * `index` parameter is the number `i` for the i-th source emission that has
  47. * happened since the subscription, starting from the number `0`.
  48. * @param {any} [thisArg] An optional argument to determine the value of `this`
  49. * in the `predicate` function.
  50. * @return {[Observable<T>, Observable<T>]} An array with two Observables: one
  51. * with values that passed the predicate, and another with values that did not
  52. * pass the predicate.
  53. */
  54. export declare function partition<T>(source: ObservableInput<T>, predicate: (value: T, index: number) => boolean, thisArg?: any): [Observable<T>, Observable<T>];