109 lines
3.6 KiB
JavaScript
109 lines
3.6 KiB
JavaScript
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import { Subscriber } from '../Subscriber';
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import { EmptyError } from '../util/EmptyError';
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/* tslint:enable:max-line-length */
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/**
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* Returns an Observable that emits only the last item emitted by the source Observable.
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* It optionally takes a predicate function as a parameter, in which case, rather than emitting
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* the last item from the source Observable, the resulting Observable will emit the last item
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* from the source Observable that satisfies the predicate.
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*
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* <img src="./img/last.png" width="100%">
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*
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* @throws {EmptyError} Delivers an EmptyError to the Observer's `error`
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* callback if the Observable completes before any `next` notification was sent.
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* @param {function} predicate - The condition any source emitted item has to satisfy.
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* @return {Observable} An Observable that emits only the last item satisfying the given condition
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* from the source, or an NoSuchElementException if no such items are emitted.
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* @throws - Throws if no items that match the predicate are emitted by the source Observable.
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* @method last
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* @owner Observable
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*/
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export function last(predicate, resultSelector, defaultValue) {
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return (source) => source.lift(new LastOperator(predicate, resultSelector, defaultValue, source));
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}
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class LastOperator {
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constructor(predicate, resultSelector, defaultValue, source) {
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this.predicate = predicate;
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this.resultSelector = resultSelector;
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this.defaultValue = defaultValue;
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this.source = source;
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}
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call(observer, source) {
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return source.subscribe(new LastSubscriber(observer, this.predicate, this.resultSelector, this.defaultValue, this.source));
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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 LastSubscriber extends Subscriber {
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constructor(destination, predicate, resultSelector, defaultValue, source) {
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super(destination);
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this.predicate = predicate;
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this.resultSelector = resultSelector;
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this.defaultValue = defaultValue;
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this.source = source;
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this.hasValue = false;
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this.index = 0;
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if (typeof defaultValue !== 'undefined') {
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this.lastValue = defaultValue;
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this.hasValue = true;
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}
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}
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_next(value) {
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const index = this.index++;
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if (this.predicate) {
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this._tryPredicate(value, index);
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}
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else {
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if (this.resultSelector) {
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this._tryResultSelector(value, index);
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return;
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}
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this.lastValue = value;
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this.hasValue = true;
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}
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}
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_tryPredicate(value, index) {
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let result;
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try {
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result = this.predicate(value, index, this.source);
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}
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catch (err) {
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this.destination.error(err);
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return;
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}
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if (result) {
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if (this.resultSelector) {
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this._tryResultSelector(value, index);
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return;
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}
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this.lastValue = value;
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this.hasValue = true;
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}
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}
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_tryResultSelector(value, index) {
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let result;
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try {
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result = this.resultSelector(value, index);
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}
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catch (err) {
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this.destination.error(err);
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return;
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}
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this.lastValue = result;
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this.hasValue = true;
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}
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_complete() {
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const destination = this.destination;
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if (this.hasValue) {
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destination.next(this.lastValue);
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destination.complete();
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}
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else {
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destination.error(new EmptyError);
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}
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}
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}
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//# sourceMappingURL=last.js.map
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