103 lines
3.8 KiB
JavaScript
103 lines
3.8 KiB
JavaScript
import { Subscriber } from '../Subscriber';
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/* tslint:enable:max-line-length */
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/**
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* Perform a side effect for every emission on the source Observable, but return
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* an Observable that is identical to the source.
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*
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* <span class="informal">Intercepts each emission on the source and runs a
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* function, but returns an output which is identical to the source as long as errors don't occur.</span>
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*
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* <img src="./img/do.png" width="100%">
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*
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* Returns a mirrored Observable of the source Observable, but modified so that
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* the provided Observer is called to perform a side effect for every value,
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* error, and completion emitted by the source. Any errors that are thrown in
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* the aforementioned Observer or handlers are safely sent down the error path
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* of the output Observable.
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*
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* This operator is useful for debugging your Observables for the correct values
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* or performing other side effects.
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*
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* Note: this is different to a `subscribe` on the Observable. If the Observable
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* returned by `do` is not subscribed, the side effects specified by the
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* Observer will never happen. `do` therefore simply spies on existing
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* execution, it does not trigger an execution to happen like `subscribe` does.
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*
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* @example <caption>Map every click to the clientX position of that click, while also logging the click event</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var positions = clicks
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* .do(ev => console.log(ev))
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* .map(ev => ev.clientX);
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* positions.subscribe(x => console.log(x));
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*
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* @see {@link map}
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* @see {@link subscribe}
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*
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* @param {Observer|function} [nextOrObserver] A normal Observer object or a
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* callback for `next`.
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* @param {function} [error] Callback for errors in the source.
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* @param {function} [complete] Callback for the completion of the source.
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* @return {Observable} An Observable identical to the source, but runs the
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* specified Observer or callback(s) for each item.
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* @name tap
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*/
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export function tap(nextOrObserver, error, complete) {
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return function tapOperatorFunction(source) {
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return source.lift(new DoOperator(nextOrObserver, error, complete));
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};
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}
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class DoOperator {
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constructor(nextOrObserver, error, complete) {
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this.nextOrObserver = nextOrObserver;
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this.error = error;
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this.complete = complete;
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}
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call(subscriber, source) {
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return source.subscribe(new DoSubscriber(subscriber, this.nextOrObserver, this.error, this.complete));
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}
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}
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/**
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* We need this JSDoc comment for affecting ESDoc.
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* @ignore
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* @extends {Ignored}
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*/
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class DoSubscriber extends Subscriber {
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constructor(destination, nextOrObserver, error, complete) {
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super(destination);
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const safeSubscriber = new Subscriber(nextOrObserver, error, complete);
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safeSubscriber.syncErrorThrowable = true;
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this.add(safeSubscriber);
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this.safeSubscriber = safeSubscriber;
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}
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_next(value) {
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const { safeSubscriber } = this;
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safeSubscriber.next(value);
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if (safeSubscriber.syncErrorThrown) {
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this.destination.error(safeSubscriber.syncErrorValue);
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}
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else {
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this.destination.next(value);
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}
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}
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_error(err) {
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const { safeSubscriber } = this;
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safeSubscriber.error(err);
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if (safeSubscriber.syncErrorThrown) {
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this.destination.error(safeSubscriber.syncErrorValue);
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}
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else {
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this.destination.error(err);
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}
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}
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_complete() {
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const { safeSubscriber } = this;
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safeSubscriber.complete();
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if (safeSubscriber.syncErrorThrown) {
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this.destination.error(safeSubscriber.syncErrorValue);
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}
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else {
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this.destination.complete();
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}
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}
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}
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//# sourceMappingURL=tap.js.map
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