work.suroh.tk/node_modules/rxjs/_esm2015/operator/concatMapTo.js

62 lines
2.8 KiB
JavaScript

import { concatMapTo as higherOrder } from '../operators/concatMapTo';
/* tslint:enable:max-line-length */
/**
* Projects each source value to the same Observable which is merged multiple
* times in a serialized fashion on the output Observable.
*
* <span class="informal">It's like {@link concatMap}, but maps each value
* always to the same inner Observable.</span>
*
* <img src="./img/concatMapTo.png" width="100%">
*
* Maps each source value to the given Observable `innerObservable` regardless
* of the source value, and then flattens those resulting Observables into one
* single Observable, which is the output Observable. Each new `innerObservable`
* instance emitted on the output Observable is concatenated with the previous
* `innerObservable` instance.
*
* __Warning:__ if source values arrive endlessly and faster than their
* corresponding inner Observables can complete, it will result in memory issues
* as inner Observables amass in an unbounded buffer waiting for their turn to
* be subscribed to.
*
* Note: `concatMapTo` is equivalent to `mergeMapTo` with concurrency parameter
* set to `1`.
*
* @example <caption>For each click event, tick every second from 0 to 3, with no concurrency</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var result = clicks.concatMapTo(Rx.Observable.interval(1000).take(4));
* result.subscribe(x => console.log(x));
*
* // Results in the following:
* // (results are not concurrent)
* // For every click on the "document" it will emit values 0 to 3 spaced
* // on a 1000ms interval
* // one click = 1000ms-> 0 -1000ms-> 1 -1000ms-> 2 -1000ms-> 3
*
* @see {@link concat}
* @see {@link concatAll}
* @see {@link concatMap}
* @see {@link mergeMapTo}
* @see {@link switchMapTo}
*
* @param {ObservableInput} innerObservable An Observable to replace each value from
* the source 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 of values merged together by joining the
* passed observable with itself, one after the other, for each value emitted
* from the source.
* @method concatMapTo
* @owner Observable
*/
export function concatMapTo(innerObservable, resultSelector) {
return higherOrder(innerObservable, resultSelector)(this);
}
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