41 lines
1.6 KiB
JavaScript
41 lines
1.6 KiB
JavaScript
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/** PURE_IMPORTS_START .._operators_defaultIfEmpty PURE_IMPORTS_END */
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import { defaultIfEmpty as higherOrder } from '../operators/defaultIfEmpty';
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/* tslint:enable:max-line-length */
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/**
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* Emits a given value if the source Observable completes without emitting any
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* `next` value, otherwise mirrors the source Observable.
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*
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* <span class="informal">If the source Observable turns out to be empty, then
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* this operator will emit a default value.</span>
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*
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* <img src="./img/defaultIfEmpty.png" width="100%">
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*
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* `defaultIfEmpty` emits the values emitted by the source Observable or a
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* specified default value if the source Observable is empty (completes without
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* having emitted any `next` value).
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*
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* @example <caption>If no clicks happen in 5 seconds, then emit "no clicks"</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var clicksBeforeFive = clicks.takeUntil(Rx.Observable.interval(5000));
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* var result = clicksBeforeFive.defaultIfEmpty('no clicks');
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* result.subscribe(x => console.log(x));
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*
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* @see {@link empty}
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* @see {@link last}
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*
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* @param {any} [defaultValue=null] The default value used if the source
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* Observable is empty.
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* @return {Observable} An Observable that emits either the specified
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* `defaultValue` if the source Observable emits no items, or the values emitted
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* by the source Observable.
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* @method defaultIfEmpty
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* @owner Observable
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*/
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export function defaultIfEmpty(defaultValue) {
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if (defaultValue === void 0) {
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defaultValue = null;
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}
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return higherOrder(defaultValue)(this);
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}
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//# sourceMappingURL=defaultIfEmpty.js.map
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