rxjs
Version:
Reactive Extensions for modern JavaScript
59 lines (55 loc) • 2.67 kB
text/typescript
import { Observable } from '../Observable';
import { PartialObserver } from '../Observer';
import { tap as higherOrder } from '../operators/tap';
/* tslint:disable:max-line-length */
export function _do<T>(this: Observable<T>, next: (x: T) => void, error?: (e: any) => void, complete?: () => void): Observable<T>;
export function _do<T>(this: Observable<T>, observer: PartialObserver<T>): Observable<T>;
/* tslint:enable:max-line-length */
/**
* Perform a side effect for every emission on the source Observable, but return
* an Observable that is identical to the source.
*
* <span class="informal">Intercepts each emission on the source and runs a
* function, but returns an output which is identical to the source as long as errors don't occur.</span>
*
* <img src="./img/do.png" width="100%">
*
* Returns a mirrored Observable of the source Observable, but modified so that
* the provided Observer is called to perform a side effect for every value,
* error, and completion emitted by the source. Any errors that are thrown in
* the aforementioned Observer or handlers are safely sent down the error path
* of the output Observable.
*
* This operator is useful for debugging your Observables for the correct values
* or performing other side effects.
*
* Note: this is different to a `subscribe` on the Observable. If the Observable
* returned by `do` is not subscribed, the side effects specified by the
* Observer will never happen. `do` therefore simply spies on existing
* execution, it does not trigger an execution to happen like `subscribe` does.
*
* @example <caption>Map every click to the clientX position of that click, while also logging the click event</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var positions = clicks
* .do(ev => console.log(ev))
* .map(ev => ev.clientX);
* positions.subscribe(x => console.log(x));
*
* @see {@link map}
* @see {@link subscribe}
*
* @param {Observer|function} [nextOrObserver] A normal Observer object or a
* callback for `next`.
* @param {function} [error] Callback for errors in the source.
* @param {function} [complete] Callback for the completion of the source.
* @return {Observable} An Observable identical to the source, but runs the
* specified Observer or callback(s) for each item.
* @method do
* @name do
* @owner Observable
*/
export function _do<T>(this: Observable<T>, nextOrObserver?: PartialObserver<T> | ((x: T) => void),
error?: (e: any) => void,
complete?: () => void): Observable<T> {
return higherOrder(<any>nextOrObserver, error, complete)(this) as Observable<T>;
}