100 lines
3.8 KiB
JavaScript
100 lines
3.8 KiB
JavaScript
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"use strict";
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var __extends = (this && this.__extends) || function (d, b) {
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for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
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function __() { this.constructor = d; }
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d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
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};
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var Subscriber_1 = require('../Subscriber');
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var ArgumentOutOfRangeError_1 = require('../util/ArgumentOutOfRangeError');
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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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* <img src="./img/elementAt.png" width="100%">
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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 <caption>Emit only the third click event</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var result = clicks.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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* @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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* ArgumentOutOrRangeError 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 {number} index Is the number `i` for the i-th source emission that has
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* happened since the subscription, starting from the number `0`.
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* @param {T} [defaultValue] The default value returned for missing indices.
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* @return {Observable} An Observable that emits a single item, if it is found.
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* Otherwise, will emit the default value if given. If not, then emits an error.
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* @method elementAt
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* @owner Observable
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*/
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function elementAt(index, defaultValue) {
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return function (source) { return source.lift(new ElementAtOperator(index, defaultValue)); };
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}
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exports.elementAt = elementAt;
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var ElementAtOperator = (function () {
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function ElementAtOperator(index, defaultValue) {
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this.index = index;
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this.defaultValue = defaultValue;
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if (index < 0) {
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throw new ArgumentOutOfRangeError_1.ArgumentOutOfRangeError;
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}
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}
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ElementAtOperator.prototype.call = function (subscriber, source) {
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return source.subscribe(new ElementAtSubscriber(subscriber, this.index, this.defaultValue));
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};
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return ElementAtOperator;
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}());
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/**
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* We need this JSDoc comment for affecting ESDoc.
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* @ignore
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* @extends {Ignored}
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*/
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var ElementAtSubscriber = (function (_super) {
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__extends(ElementAtSubscriber, _super);
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function ElementAtSubscriber(destination, index, defaultValue) {
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_super.call(this, destination);
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this.index = index;
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this.defaultValue = defaultValue;
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}
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ElementAtSubscriber.prototype._next = function (x) {
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if (this.index-- === 0) {
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this.destination.next(x);
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this.destination.complete();
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}
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};
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ElementAtSubscriber.prototype._complete = function () {
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var destination = this.destination;
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if (this.index >= 0) {
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if (typeof this.defaultValue !== 'undefined') {
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destination.next(this.defaultValue);
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}
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else {
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destination.error(new ArgumentOutOfRangeError_1.ArgumentOutOfRangeError);
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}
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}
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destination.complete();
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};
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return ElementAtSubscriber;
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}(Subscriber_1.Subscriber));
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//# sourceMappingURL=elementAt.js.map
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