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