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- import { Observable } from '../Observable';
- /**
- * Emits the single value at the specified `index` in a sequence of emissions
- * from the source Observable.
- *
- * <span class="informal">Emits only the i-th value, then completes.</span>
- *
- * <img src="./img/elementAt.png" width="100%">
- *
- * `elementAt` returns an Observable that emits the item at the specified
- * `index` in the source Observable, or a default value if that `index` is out
- * of range and the `default` argument is provided. If the `default` argument is
- * not given and the `index` is out of range, the output Observable will emit an
- * `ArgumentOutOfRangeError` error.
- *
- * @example <caption>Emit only the third click event</caption>
- * var clicks = Rx.Observable.fromEvent(document, 'click');
- * var result = clicks.elementAt(2);
- * result.subscribe(x => console.log(x));
- *
- * // Results in:
- * // click 1 = nothing
- * // click 2 = nothing
- * // click 3 = MouseEvent object logged to console
- *
- * @see {@link first}
- * @see {@link last}
- * @see {@link skip}
- * @see {@link single}
- * @see {@link take}
- *
- * @throws {ArgumentOutOfRangeError} When using `elementAt(i)`, it delivers an
- * ArgumentOutOrRangeError to the Observer's `error` callback if `i < 0` or the
- * Observable has completed before emitting the i-th `next` notification.
- *
- * @param {number} index Is the number `i` for the i-th source emission that has
- * happened since the subscription, starting from the number `0`.
- * @param {T} [defaultValue] The default value returned for missing indices.
- * @return {Observable} An Observable that emits a single item, if it is found.
- * Otherwise, will emit the default value if given. If not, then emits an error.
- * @method elementAt
- * @owner Observable
- */
- export declare function elementAt<T>(this: Observable<T>, index: number, defaultValue?: T): Observable<T>;
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