DMleadgen
46d973904b
Next.js website for Rocky Mountain Vending company featuring: - Product catalog with Stripe integration - Service areas and parts pages - Admin dashboard with Clerk authentication - SEO optimized pages with JSON-LD structured data Co-authored-by: Cursor <cursoragent@cursor.com>
68 lines
2.4 KiB
Text
68 lines
2.4 KiB
Text
import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError';
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import { Observable } from '../Observable';
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import { OperatorFunction } from '../types';
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import { filter } from './filter';
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import { throwIfEmpty } from './throwIfEmpty';
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import { defaultIfEmpty } from './defaultIfEmpty';
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import { take } from './take';
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/**
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* Emits the single value at the specified `index` in a sequence of emissions
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* from the source Observable.
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*
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* <span class="informal">Emits only the i-th value, then completes.</span>
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*
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* 
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*
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* `elementAt` returns an Observable that emits the item at the specified
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* `index` in the source Observable, or a default value if that `index` is out
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* of range and the `default` argument is provided. If the `default` argument is
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* not given and the `index` is out of range, the output Observable will emit an
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* `ArgumentOutOfRangeError` error.
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*
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* ## Example
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*
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* Emit only the third click event
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*
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* ```ts
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* import { fromEvent, elementAt } from 'rxjs';
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*
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* const clicks = fromEvent(document, 'click');
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* const result = clicks.pipe(elementAt(2));
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* result.subscribe(x => console.log(x));
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*
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* // Results in:
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* // click 1 = nothing
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* // click 2 = nothing
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* // click 3 = MouseEvent object logged to console
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* ```
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*
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* @see {@link first}
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* @see {@link last}
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* @see {@link skip}
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* @see {@link single}
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* @see {@link take}
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*
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* @throws {ArgumentOutOfRangeError} When using `elementAt(i)`, it delivers an
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* `ArgumentOutOfRangeError` to the Observer's `error` callback if `i < 0` or the
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* Observable has completed before emitting the i-th `next` notification.
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*
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* @param index Is the number `i` for the i-th source emission that has happened
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* since the subscription, starting from the number `0`.
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* @param defaultValue The default value returned for missing indices.
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* @return A function that returns an Observable that emits a single item, if
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* it is found. Otherwise, it will emit the default value if given. If not, it
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* emits an error.
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*/
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export function elementAt<T, D = T>(index: number, defaultValue?: D): OperatorFunction<T, T | D> {
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if (index < 0) {
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throw new ArgumentOutOfRangeError();
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}
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const hasDefaultValue = arguments.length >= 2;
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return (source: Observable<T>) =>
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source.pipe(
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filter((v, i) => i === index),
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take(1),
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hasDefaultValue ? defaultIfEmpty(defaultValue!) : throwIfEmpty(() => new ArgumentOutOfRangeError())
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);
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}
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