@reactivex/rxjs
Version:
Reactive Extensions for modern JavaScript
141 lines • 5.3 kB
JavaScript
;
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 innerSubscribe_1 = require("../innerSubscribe");
/**
* 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.
*
* ## Examples
* A simple example with numbers
* ```ts
* import { of } from 'rxjs';
* import { distinct } from 'rxjs/operators';
*
* of(1, 1, 2, 2, 2, 1, 2, 3, 4, 3, 2, 1).pipe(
* distinct(),
* )
* .subscribe(x => console.log(x)); // 1, 2, 3, 4
* ```
*
* An example using a keySelector function
* ```typescript
* import { of } from 'rxjs';
* import { distinct } from 'rxjs/operators';
*
* interface Person {
* age: number,
* name: string
* }
*
* of<Person>(
* { age: 4, name: 'Foo'},
* { age: 7, name: 'Bar'},
* { age: 5, name: 'Foo'},
* ).pipe(
* distinct((p: Person) => p.name),
* )
* .subscribe(x => console.log(x));
*
* // displays:
* // { age: 4, name: 'Foo' }
* // { age: 7, name: 'Bar' }
* ```
* @see {@link distinctUntilChanged}
* @see {@link distinctUntilKeyChanged}
*
* @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
*/
function distinct(keySelector, flushes) {
return function (source) { return source.lift(new DistinctOperator(keySelector, flushes)); };
}
exports.distinct = distinct;
var DistinctOperator = /** @class */ (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}
*/
var DistinctSubscriber = /** @class */ (function (_super) {
__extends(DistinctSubscriber, _super);
function DistinctSubscriber(destination, keySelector, flushes) {
var _this = _super.call(this, destination) || this;
_this.keySelector = keySelector;
_this.values = new Set();
if (flushes) {
_this.add(innerSubscribe_1.innerSubscribe(flushes, new innerSubscribe_1.SimpleInnerSubscriber(_this)));
}
return _this;
}
DistinctSubscriber.prototype.notifyNext = function () {
this.values.clear();
};
DistinctSubscriber.prototype.notifyError = function (error) {
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;
}(innerSubscribe_1.SimpleOuterSubscriber));
exports.DistinctSubscriber = DistinctSubscriber;
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