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39 lines
1.8 KiB
39 lines
1.8 KiB
2 years ago
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import { Observable } from '../Observable';
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/**
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* Emits values emitted by the source Observable so long as each value satisfies
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* the given `predicate`, and then completes as soon as this `predicate` is not
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* satisfied.
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*
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* <span class="informal">Takes values from the source only while they pass the
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* condition given. When the first value does not satisfy, it completes.</span>
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*
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* <img src="./img/takeWhile.png" width="100%">
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*
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* `takeWhile` subscribes and begins mirroring the source Observable. Each value
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* emitted on the source is given to the `predicate` function which returns a
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* boolean, representing a condition to be satisfied by the source values. The
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* output Observable emits the source values until such time as the `predicate`
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* returns false, at which point `takeWhile` stops mirroring the source
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* Observable and completes the output Observable.
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*
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* @example <caption>Emit click events only while the clientX property is greater than 200</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var result = clicks.takeWhile(ev => ev.clientX > 200);
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* result.subscribe(x => console.log(x));
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*
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* @see {@link take}
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* @see {@link takeLast}
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* @see {@link takeUntil}
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* @see {@link skip}
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*
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* @param {function(value: T, index: number): boolean} predicate A function that
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* evaluates a value emitted by the source Observable and returns a boolean.
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* Also takes the (zero-based) index as the second argument.
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* @return {Observable<T>} An Observable that emits the values from the source
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* Observable so long as each value satisfies the condition defined by the
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* `predicate`, then completes.
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* @method takeWhile
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* @owner Observable
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*/
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export declare function takeWhile<T>(this: Observable<T>, predicate: (value: T, index: number) => boolean): Observable<T>;
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