es6/operator/distinct.js

import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
import { Set } from '../util/Set';
/**
 * Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from previous items.
 * If a keySelector function is provided, then it will project each value from the source observable into a new value that it will
 * check for equality with previously projected values. If a keySelector function is not provided, it will use each value from the
 * source observable directly with an equality check against previous values.
 * In JavaScript runtimes that support `Set`, this operator will use a `Set` to improve performance of the distinct value checking.
 * In other runtimes, this operator will use a minimal implementation of `Set` that relies on an `Array` and `indexOf` under the
 * hood, so performance will degrade as more values are checked for distinction. Even in newer browsers, a long-running `distinct`
 * use might result in memory leaks. To help alleviate this in some scenarios, an optional `flushes` parameter is also provided so
 * that the internal `Set` can be "flushed", basically clearing it of values.
 * @param {function} [keySelector] optional function to select which value you want to check as distinct.
 * @param {Observable} [flushes] optional Observable for flushing the internal HashSet of the operator.
 * @return {Observable} an Observable that emits items from the source Observable with distinct values.
 * @method distinct
 * @owner Observable
 */
export function distinct(keySelector, flushes) {
    return this.lift(new DistinctOperator(keySelector, flushes));
}
var DistinctOperator = (function () {
    function DistinctOperator(keySelector, flushes) {
        this.keySelector = keySelector;
        this.flushes = flushes;
    }
    DistinctOperator.prototype.call = function (subscriber, source) {
        return source._subscribe(new DistinctSubscriber(subscriber, this.keySelector, this.flushes));
    };
    return DistinctOperator;
}());
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
export var DistinctSubscriber = (function (_super) {
    __extends(DistinctSubscriber, _super);
    function DistinctSubscriber(destination, keySelector, flushes) {
        _super.call(this, destination);
        this.keySelector = keySelector;
        this.values = new Set();
        if (flushes) {
            this.add(subscribeToResult(this, flushes));
        }
    }
    DistinctSubscriber.prototype.notifyNext = function (outerValue, innerValue, outerIndex, innerIndex, innerSub) {
        this.values.clear();
    };
    DistinctSubscriber.prototype.notifyError = function (error, innerSub) {
        this._error(error);
    };
    DistinctSubscriber.prototype._next = function (value) {
        if (this.keySelector) {
            this._useKeySelector(value);
        }
        else {
            this._finalizeNext(value, value);
        }
    };
    DistinctSubscriber.prototype._useKeySelector = function (value) {
        var key;
        var destination = this.destination;
        try {
            key = this.keySelector(value);
        }
        catch (err) {
            destination.error(err);
            return;
        }
        this._finalizeNext(key, value);
    };
    DistinctSubscriber.prototype._finalizeNext = function (key, value) {
        var values = this.values;
        if (!values.has(key)) {
            values.add(key);
            this.destination.next(value);
        }
    };
    return DistinctSubscriber;
}(OuterSubscriber));
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