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PATH: usr / local / lib / node_modules / ghost-cli / node_modules / rxjs / src / internal / operators

import { Operator } from '../Operator';
import { Subscriber } from '../Subscriber';
import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError';
import { Observable } from '../Observable';
import { MonoTypeOperatorFunction, TeardownLogic } from '../types';
import { filter } from './filter';
import { throwIfEmpty } from './throwIfEmpty';
import { defaultIfEmpty } from './defaultIfEmpty';
import { take } from './take';

/**
 * 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>
 *
 * ![](elementAt.png)
 *
 * `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
 * Emit only the third click event
 * ```ts
 * import { fromEvent } from 'rxjs';
 * import { elementAt } from 'rxjs/operators';
 *
 * const clicks = fromEvent(document, 'click');
 * const result = clicks.pipe(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 function elementAt<T>(index: number, defaultValue?: T): MonoTypeOperatorFunction<T> {
  if (index < 0) { throw new ArgumentOutOfRangeError(); }
  const hasDefaultValue = arguments.length >= 2;
  return (source: Observable<T>) => source.pipe(
    filter((v, i) => i === index),
    take(1),
    hasDefaultValue
      ? defaultIfEmpty(defaultValue)
      : throwIfEmpty(() => new ArgumentOutOfRangeError()),
  );
}

[-] toArray.ts [edit]
[-] window.ts [edit]
[-] retry.ts [edit]
[-] mergeAll.ts [edit]
[-] windowWhen.ts [edit]
[-] every.ts [edit]
[-] timeout.ts [edit]
[-] debounceTime.ts [edit]
[-] index.ts [edit]
[-] takeWhile.ts [edit]
[-] audit.ts [edit]
[-] reduce.ts [edit]
[-] mapTo.ts [edit]
[-] count.ts [edit]
[-] debounce.ts [edit]
[-] throwIfEmpty.ts [edit]
[-] auditTime.ts [edit]
[-] scan.ts [edit]
[-] switchAll.ts [edit]
[-] map.ts [edit]
[-] bufferCount.ts [edit]
[-] mergeScan.ts [edit]
[-] publish.ts [edit]
[-] min.ts [edit]
[+] ..
[-] publishReplay.ts [edit]
[-] bufferTime.ts [edit]
[-] share.ts [edit]
[-] repeat.ts [edit]
[-] distinct.ts [edit]
[-] concatMapTo.ts [edit]
[-] buffer.ts [edit]
[-] concatMap.ts [edit]
[-] max.ts [edit]
[-] partition.ts [edit]
[-] observeOn.ts [edit]
[-] bufferWhen.ts [edit]
[-] dematerialize.ts [edit]
[-] throttle.ts [edit]
[-] groupBy.ts [edit]
[-] withLatestFrom.ts [edit]
[-] exhaust.ts [edit]
[-] exhaustMap.ts [edit]
[-] retryWhen.ts [edit]
[-] zipAll.ts [edit]
[-] find.ts [edit]
[-] mergeMap.ts [edit]
[-] single.ts [edit]
[-] last.ts [edit]
[-] combineLatest.ts [edit]
[-] publishLast.ts [edit]
[-] pluck.ts [edit]
[-] pairwise.ts [edit]
[-] distinctUntilChanged.ts [edit]
[-] timeInterval.ts [edit]
[-] shareReplay.ts [edit]
[-] skipUntil.ts [edit]
[-] findIndex.ts [edit]
[-] windowToggle.ts [edit]
[-] startWith.ts [edit]
[-] timeoutWith.ts [edit]
[-] concat.ts [edit]
[-] materialize.ts [edit]
[-] timestamp.ts [edit]
[-] onErrorResumeNext.ts [edit]
[-] subscribeOn.ts [edit]
[-] takeUntil.ts [edit]
[-] skipLast.ts [edit]
[-] throttleTime.ts [edit]
[-] mergeMapTo.ts [edit]
[-] multicast.ts [edit]
[-] merge.ts [edit]
[-] takeLast.ts [edit]
[-] delayWhen.ts [edit]
[-] sampleTime.ts [edit]
[-] tap.ts [edit]
[-] take.ts [edit]
[-] sample.ts [edit]
[-] filter.ts [edit]
[-] skip.ts [edit]
[-] expand.ts [edit]
[-] publishBehavior.ts [edit]
[-] sequenceEqual.ts [edit]
[-] ignoreElements.ts [edit]
[-] catchError.ts [edit]
[-] endWith.ts [edit]
[-] refCount.ts [edit]
[-] windowCount.ts [edit]
[-] defaultIfEmpty.ts [edit]
[-] windowTime.ts [edit]
[-] switchMapTo.ts [edit]
[-] switchMap.ts [edit]
[-] delay.ts [edit]
[-] bufferToggle.ts [edit]
[-] repeatWhen.ts [edit]
[-] concatAll.ts [edit]
[-] first.ts [edit]
[-] zip.ts [edit]
[-] elementAt.ts [edit]
[-] skipWhile.ts [edit]
[-] race.ts [edit]
[-] finalize.ts [edit]
[-] combineAll.ts [edit]
[-] distinctUntilKeyChanged.ts [edit]
[-] isEmpty.ts [edit]