94 lines
3.5 KiB
JavaScript
94 lines
3.5 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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/* tslint:enable:max-line-length */
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/**
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* Filter items emitted by the source Observable by only emitting those that
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* satisfy a specified predicate.
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*
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* <span class="informal">Like
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* [Array.prototype.filter()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter),
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* it only emits a value from the source if it passes a criterion function.</span>
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*
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* <img src="./img/filter.png" width="100%">
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*
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* Similar to the well-known `Array.prototype.filter` method, this operator
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* takes values from the source Observable, passes them through a `predicate`
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* function and only emits those values that yielded `true`.
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*
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* @example <caption>Emit only click events whose target was a DIV element</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var clicksOnDivs = clicks.filter(ev => ev.target.tagName === 'DIV');
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* clicksOnDivs.subscribe(x => console.log(x));
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*
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* @see {@link distinct}
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* @see {@link distinctUntilChanged}
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* @see {@link distinctUntilKeyChanged}
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* @see {@link ignoreElements}
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* @see {@link partition}
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* @see {@link skip}
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*
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* @param {function(value: T, index: number): boolean} predicate A function that
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* evaluates each value emitted by the source Observable. If it returns `true`,
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* the value is emitted, if `false` the value is not passed to the output
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* Observable. The `index` parameter is the number `i` for the i-th source
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* emission that has happened since the subscription, starting from the number
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* `0`.
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* @param {any} [thisArg] An optional argument to determine the value of `this`
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* in the `predicate` function.
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* @return {Observable} An Observable of values from the source that were
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* allowed by the `predicate` function.
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* @method filter
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* @owner Observable
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*/
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function filter(predicate, thisArg) {
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return function filterOperatorFunction(source) {
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return source.lift(new FilterOperator(predicate, thisArg));
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};
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}
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exports.filter = filter;
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var FilterOperator = (function () {
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function FilterOperator(predicate, thisArg) {
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this.predicate = predicate;
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this.thisArg = thisArg;
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}
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FilterOperator.prototype.call = function (subscriber, source) {
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return source.subscribe(new FilterSubscriber(subscriber, this.predicate, this.thisArg));
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};
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return FilterOperator;
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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 FilterSubscriber = (function (_super) {
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__extends(FilterSubscriber, _super);
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function FilterSubscriber(destination, predicate, thisArg) {
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_super.call(this, destination);
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this.predicate = predicate;
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this.thisArg = thisArg;
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this.count = 0;
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}
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// the try catch block below is left specifically for
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// optimization and perf reasons. a tryCatcher is not necessary here.
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FilterSubscriber.prototype._next = function (value) {
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var result;
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try {
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result = this.predicate.call(this.thisArg, value, this.count++);
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}
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catch (err) {
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this.destination.error(err);
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return;
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}
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if (result) {
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this.destination.next(value);
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}
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};
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return FilterSubscriber;
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}(Subscriber_1.Subscriber));
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//# sourceMappingURL=filter.js.map
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