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37 lines
1.6 KiB
37 lines
1.6 KiB
2 years ago
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import { Observable } from '../Observable';
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/**
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* Emits only the index of the first value emitted by the source Observable that
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* meets some condition.
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*
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* <span class="informal">It's like {@link find}, but emits the index of the
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* found value, not the value itself.</span>
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*
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* <img src="./img/findIndex.png" width="100%">
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*
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* `findIndex` searches for the first item in the source Observable that matches
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* the specified condition embodied by the `predicate`, and returns the
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* (zero-based) index of the first occurrence in the source. Unlike
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* {@link first}, the `predicate` is required in `findIndex`, and does not emit
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* an error if a valid value is not found.
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*
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* @example <caption>Emit the index of first click that happens on a DIV element</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var result = clicks.findIndex(ev => ev.target.tagName === 'DIV');
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* result.subscribe(x => console.log(x));
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*
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* @see {@link filter}
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* @see {@link find}
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* @see {@link first}
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* @see {@link take}
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*
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* @param {function(value: T, index: number, source: Observable<T>): boolean} predicate
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* A function called with each item to test for condition matching.
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* @param {any} [thisArg] An optional argument to determine the value of `this`
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* in the `predicate` function.
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* @return {Observable} An Observable of the index of the first item that
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* matches the condition.
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* @method find
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* @owner Observable
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*/
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export declare function findIndex<T>(this: Observable<T>, predicate: (value: T, index: number, source: Observable<T>) => boolean, thisArg?: any): Observable<number>;
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