- Maps values to a new observable on emission from source, subscribing to and emitting results of inner observables
- By default mergeMap does not limit the number of active inner observables
- Useful for HTTP requests you do not want cancelled, such as POSTs
- Inner observables whose lifetime you mill manage
- [X] Remember to clean up inner observable
import { fromEvent, interval } from 'rxjs';
import { ajax } from 'rxjs/ajax';
import {
mergeMap,
catchError,
takeUntil,
map
} from 'rxjs/operators';
/*
* BEGIN FIRST SECTION
*/
const interval$ = interval(1000);
const click$ = fromEvent(document, 'click');
/*
* mergeMap invokes the function you provide,
* subscribing to each returned observable internally.
* Any values emitted by these inner observables
* are then emitted by mergeMap. By default there
* is no limit to the number of active inner
* subscriptions that can be active at a time
* with mergeMap, so if you continually click on
* the page more and more timers will be activated.
* This can be dangerous if you have long
* running inner observables and forget to clean
* them up.
*/
click$.pipe(
mergeMap(() => interval$)
).subscribe(console.log);
const mousedown$ = fromEvent(document, 'mousedown');
const mouseup$ = fromEvent(document, 'mouseup');
/*
* In this case, we are mapping to a new interval
* observable on mousedown, but we are limiting it's
* lifetime by using the takeUntil operator with
* the mouseup$ stream.
*/
mousedown$.pipe(
mergeMap(() => interval$.pipe(
takeUntil(mouseup$)
))
).subscribe(console.log);
const coordinates$ = click$.pipe(
map((event: any) => ({
x: event.clientX,
y: event.clientY
}))
);
/*
* mergeMap is good for 'fire and forget' save request
* you do not want to be cancelled. For instance, in this
* example we are emulating a save of coordinates
* anytime the user clicks on the page.
*/
const coordinatesWithSave$ = coordinates$.pipe(
mergeMap(coords => ajax.post(
'https://www.mocky.io/v2/5185415ba171ea3a00704eed'
))
);
coordinatesWithSave$.subscribe(console.log);
原文地址:http://www.cnblogs.com/Answer1215/p/16806360.html
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