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

64 lines
2.6 KiB
JavaScript

import { mergeMap as higherOrderMergeMap } from '../operators/mergeMap';
/* tslint:enable:max-line-length */
/**
* Projects each source value to an Observable which is merged in the output
* Observable.
*
* <span class="informal">Maps each value to an Observable, then flattens all of
* these inner Observables using {@link mergeAll}.</span>
*
* <img src="./img/mergeMap.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 Observable, and then merging those resulting Observables and
* emitting the results of this merger.
*
* @example <caption>Map and flatten each letter to an Observable ticking every 1 second</caption>
* var letters = Rx.Observable.of('a', 'b', 'c');
* var result = letters.mergeMap(x =>
* Rx.Observable.interval(1000).map(i => x+i)
* );
* result.subscribe(x => console.log(x));
*
* // Results in the following:
* // a0
* // b0
* // c0
* // a1
* // b1
* // c1
* // continues to list a,b,c with respective ascending integers
*
* @see {@link concatMap}
* @see {@link exhaustMap}
* @see {@link merge}
* @see {@link mergeAll}
* @see {@link mergeMapTo}
* @see {@link mergeScan}
* @see {@link switchMap}
*
* @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
* @param {number} [concurrent=Number.POSITIVE_INFINITY] Maximum number of input
* Observables being subscribed to concurrently.
* @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 merging the results of the Observables obtained
* from this transformation.
* @method mergeMap
* @owner Observable
*/
export function mergeMap(project, resultSelector, concurrent = Number.POSITIVE_INFINITY) {
return higherOrderMergeMap(project, resultSelector, concurrent)(this);
}
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