1 import { not } from '../util/not';
2 import { subscribeTo } from '../util/subscribeTo';
3 import { filter } from '../operators/filter';
4 import { ObservableInput } from '../types';
5 import { Observable } from '../Observable';
8 * Splits the source Observable into two, one with values that satisfy a
9 * predicate, and another with values that don't satisfy the predicate.
11 * <span class="informal">It's like {@link filter}, but returns two Observables:
12 * one like the output of {@link filter}, and the other with values that did not
13 * pass the condition.</span>
17 * `partition` outputs an array with two Observables that partition the values
18 * from the source Observable through the given `predicate` function. The first
19 * Observable in that array emits source values for which the predicate argument
20 * returns true. The second Observable emits source values for which the
21 * predicate returns false. The first behaves like {@link filter} and the second
22 * behaves like {@link filter} with the predicate negated.
25 * Partition a set of numbers into odds and evens observables
27 * import { of, partition } from 'rxjs';
29 * const observableValues = of(1, 2, 3, 4, 5, 6);
30 * const [evens$, odds$] = partition(observableValues, (value, index) => value % 2 === 0);
32 * odds$.subscribe(x => console.log('odds', x));
33 * evens$.subscribe(x => console.log('evens', x));
46 * @param {function(value: T, index: number): boolean} predicate A function that
47 * evaluates each value emitted by the source Observable. If it returns `true`,
48 * the value is emitted on the first Observable in the returned array, if
49 * `false` the value is emitted on the second Observable in the array. The
50 * `index` parameter is the number `i` for the i-th source emission that has
51 * happened since the subscription, starting from the number `0`.
52 * @param {any} [thisArg] An optional argument to determine the value of `this`
53 * in the `predicate` function.
54 * @return {[Observable<T>, Observable<T>]} An array with two Observables: one
55 * with values that passed the predicate, and another with values that did not
58 export function partition<T>(
59 source: ObservableInput<T>,
60 predicate: (value: T, index: number) => boolean,
62 ): [Observable<T>, Observable<T>] {
64 filter(predicate, thisArg)(new Observable<T>(subscribeTo(source))),
65 filter(not(predicate, thisArg) as any)(new Observable<T>(subscribeTo(source)))
66 ] as [Observable<T>, Observable<T>];