81 lines
2.5 KiB
JavaScript
81 lines
2.5 KiB
JavaScript
import { Subscriber } from '../Subscriber';
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import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError';
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import { EmptyObservable } from '../observable/EmptyObservable';
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/**
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* Emits only the first `count` values emitted by the source Observable.
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*
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* <span class="informal">Takes the first `count` values from the source, then
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* completes.</span>
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*
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* <img src="./img/take.png" width="100%">
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*
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* `take` returns an Observable that emits only the first `count` values emitted
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* by the source Observable. If the source emits fewer than `count` values then
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* all of its values are emitted. After that, it completes, regardless if the
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* source completes.
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*
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* @example <caption>Take the first 5 seconds of an infinite 1-second interval Observable</caption>
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* var interval = Rx.Observable.interval(1000);
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* var five = interval.take(5);
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* five.subscribe(x => console.log(x));
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*
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* @see {@link takeLast}
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* @see {@link takeUntil}
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* @see {@link takeWhile}
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* @see {@link skip}
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*
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* @throws {ArgumentOutOfRangeError} When using `take(i)`, it delivers an
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* ArgumentOutOrRangeError to the Observer's `error` callback if `i < 0`.
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*
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* @param {number} count The maximum number of `next` values to emit.
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* @return {Observable<T>} An Observable that emits only the first `count`
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* values emitted by the source Observable, or all of the values from the source
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* if the source emits fewer than `count` values.
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* @method take
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* @owner Observable
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*/
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export function take(count) {
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return (source) => {
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if (count === 0) {
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return new EmptyObservable();
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}
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else {
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return source.lift(new TakeOperator(count));
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}
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};
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}
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class TakeOperator {
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constructor(total) {
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this.total = total;
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if (this.total < 0) {
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throw new ArgumentOutOfRangeError;
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}
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}
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call(subscriber, source) {
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return source.subscribe(new TakeSubscriber(subscriber, this.total));
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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 TakeSubscriber extends Subscriber {
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constructor(destination, total) {
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super(destination);
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this.total = total;
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this.count = 0;
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}
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_next(value) {
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const total = this.total;
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const count = ++this.count;
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if (count <= total) {
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this.destination.next(value);
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if (count === total) {
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this.destination.complete();
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this.unsubscribe();
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}
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}
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}
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}
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//# sourceMappingURL=take.js.map
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