biobulkbende.org/node_modules/rxjs/_esm2015/operator/switchMap.js
2020-09-16 14:23:28 +02:00

53 lines
2.6 KiB
JavaScript

import { switchMap as higherOrderSwitchMap } from '../operators/switchMap';
/* tslint:enable:max-line-length */
/**
* Projects each source value to an Observable which is merged in the output
* Observable, emitting values only from the most recently projected Observable.
*
* <span class="informal">Maps each value to an Observable, then flattens all of
* these inner Observables using {@link switch}.</span>
*
* <img src="./img/switchMap.png" width="100%">
*
* Returns an Observable that emits items based on applying a function that you
* supply to each item emitted by the source Observable, where that function
* returns an (so-called "inner") Observable. Each time it observes one of these
* inner Observables, the output Observable begins emitting the items emitted by
* that inner Observable. When a new inner Observable is emitted, `switchMap`
* stops emitting items from the earlier-emitted inner Observable and begins
* emitting items from the new one. It continues to behave like this for
* subsequent inner Observables.
*
* @example <caption>Rerun an interval Observable on every click event</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var result = clicks.switchMap((ev) => Rx.Observable.interval(1000));
* result.subscribe(x => console.log(x));
*
* @see {@link concatMap}
* @see {@link exhaustMap}
* @see {@link mergeMap}
* @see {@link switch}
* @see {@link switchMapTo}
*
* @param {function(value: T, ?index: number): ObservableInput} project A function
* that, when applied to an item emitted by the source Observable, returns an
* Observable.
* @param {function(outerValue: T, innerValue: I, outerIndex: number, innerIndex: number): any} [resultSelector]
* A function to produce the value on the output Observable based on the values
* and the indices of the source (outer) emission and the inner Observable
* emission. The arguments passed to this function are:
* - `outerValue`: the value that came from the source
* - `innerValue`: the value that came from the projected Observable
* - `outerIndex`: the "index" of the value that came from the source
* - `innerIndex`: the "index" of the value from the projected Observable
* @return {Observable} An Observable that emits the result of applying the
* projection function (and the optional `resultSelector`) to each item emitted
* by the source Observable and taking only the values from the most recently
* projected inner Observable.
* @method switchMap
* @owner Observable
*/
export function switchMap(project, resultSelector) {
return higherOrderSwitchMap(project, resultSelector)(this);
}
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