| import { Subscriber } from '../Subscriber'; |
| import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError'; |
| /** |
| * 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 function elementAt(index, defaultValue) { |
| return (source) => source.lift(new ElementAtOperator(index, defaultValue)); |
| } |
| class ElementAtOperator { |
| constructor(index, defaultValue) { |
| this.index = index; |
| this.defaultValue = defaultValue; |
| if (index < 0) { |
| throw new ArgumentOutOfRangeError; |
| } |
| } |
| call(subscriber, source) { |
| return source.subscribe(new ElementAtSubscriber(subscriber, this.index, this.defaultValue)); |
| } |
| } |
| /** |
| * We need this JSDoc comment for affecting ESDoc. |
| * @ignore |
| * @extends {Ignored} |
| */ |
| class ElementAtSubscriber extends Subscriber { |
| constructor(destination, index, defaultValue) { |
| super(destination); |
| this.index = index; |
| this.defaultValue = defaultValue; |
| } |
| _next(x) { |
| if (this.index-- === 0) { |
| this.destination.next(x); |
| this.destination.complete(); |
| } |
| } |
| _complete() { |
| const destination = this.destination; |
| if (this.index >= 0) { |
| if (typeof this.defaultValue !== 'undefined') { |
| destination.next(this.defaultValue); |
| } |
| else { |
| destination.error(new ArgumentOutOfRangeError); |
| } |
| } |
| destination.complete(); |
| } |
| } |
| //# sourceMappingURL=elementAt.js.map |