@reactivex/rxjs/dist-compat/cjs/src/internal/operators/count.js

Reactive Extensions for modern JavaScript

"use strict";
var __extends = (this && this.__extends) || (function () {
    var extendStatics = function (d, b) {
        extendStatics = Object.setPrototypeOf ||
            ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
            function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
        return extendStatics(d, b);
    }
    return function (d, b) {
        extendStatics(d, b);
        function __() { this.constructor = d; }
        d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
    };
})();
Object.defineProperty(exports, "__esModule", { value: true });
var Subscriber_1 = require("../Subscriber");
/**
 * Counts the number of emissions on the source and emits that number when the
 * source completes.
 *
 * <span class="informal">Tells how many values were emitted, when the source
 * completes.</span>
 *
 * ![](count.png)
 *
 * `count` transforms an Observable that emits values into an Observable that
 * emits a single value that represents the number of values emitted by the
 * source Observable. If the source Observable terminates with an error, `count`
 * will pass this error notification along without emitting a value first. If
 * the source Observable does not terminate at all, `count` will neither emit
 * a value nor terminate. This operator takes an optional `predicate` function
 * as argument, in which case the output emission will represent the number of
 * source values that matched `true` with the `predicate`.
 *
 * ## Examples
 *
 * Counts how many seconds have passed before the first click happened
 * ```ts
 * import { fromEvent, interval } from 'rxjs';
 * import { count, takeUntil } from 'rxjs/operators';
 *
 * const seconds = interval(1000);
 * const clicks = fromEvent(document, 'click');
 * const secondsBeforeClick = seconds.pipe(takeUntil(clicks));
 * const result = secondsBeforeClick.pipe(count());
 * result.subscribe(x => console.log(x));
 * ```
 *
 * Counts how many odd numbers are there between 1 and 7
 * ```ts
 * import { range } from 'rxjs';
 * import { count } from 'rxjs/operators';
 *
 * const numbers = range(1, 7);
 * const result = numbers.pipe(count(i => i % 2 === 1));
 * result.subscribe(x => console.log(x));
 * // Results in:
 * // 4
 * ```
 *
 * @see {@link max}
 * @see {@link min}
 * @see {@link reduce}
 *
 * @param {function(value: T, i: number, source: Observable<T>): boolean} [predicate] A
 * boolean function to select what values are to be counted. It is provided with
 * arguments of:
 * - `value`: the value from the source Observable.
 * - `index`: the (zero-based) "index" of the value from the source Observable.
 * - `source`: the source Observable instance itself.
 * @return {Observable} An Observable of one number that represents the count as
 * described above.
 * @method count
 * @owner Observable
 */
function count(predicate) {
    return function (source) { return source.lift(new CountOperator(predicate, source)); };
}
exports.count = count;
var CountOperator = /** @class */ (function () {
    function CountOperator(predicate, source) {
        this.predicate = predicate;
        this.source = source;
    }
    CountOperator.prototype.call = function (subscriber, source) {
        return source.subscribe(new CountSubscriber(subscriber, this.predicate, this.source));
    };
    return CountOperator;
}());
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
var CountSubscriber = /** @class */ (function (_super) {
    __extends(CountSubscriber, _super);
    function CountSubscriber(destination, predicate, source) {
        var _this = _super.call(this, destination) || this;
        _this.predicate = predicate;
        _this.source = source;
        _this.count = 0;
        _this.index = 0;
        return _this;
    }
    CountSubscriber.prototype._next = function (value) {
        if (this.predicate) {
            this._tryPredicate(value);
        }
        else {
            this.count++;
        }
    };
    CountSubscriber.prototype._tryPredicate = function (value) {
        var result;
        try {
            result = this.predicate(value, this.index++, this.source);
        }
        catch (err) {
            this.destination.error(err);
            return;
        }
        if (result) {
            this.count++;
        }
    };
    CountSubscriber.prototype._complete = function () {
        this.destination.next(this.count);
        this.destination.complete();
    };
    return CountSubscriber;
}(Subscriber_1.Subscriber));
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