@reactivex/rxjs
Version:
Reactive Extensions for modern JavaScript
133 lines • 4.58 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 Subscriber_1 = require("../Subscriber");
/* tslint:enable:max-line-length */
/**
* Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from the previous item.
*
* If a comparator function is provided, then it will be called for each item to test for whether or not that value should be emitted.
*
* If a comparator function is not provided, an equality check is used by default.
*
* ## Example
* A simple example with numbers
* ```ts
* import { of } from 'rxjs';
* import { distinctUntilChanged } from 'rxjs/operators';
*
* of(1, 1, 2, 2, 2, 1, 1, 2, 3, 3, 4).pipe(
* distinctUntilChanged(),
* )
* .subscribe(x => console.log(x)); // 1, 2, 1, 2, 3, 4
* ```
*
* An example using a compare function
* ```typescript
* import { of } from 'rxjs';
* import { distinctUntilChanged } from 'rxjs/operators';
*
* interface Person {
* age: number,
* name: string
* }
*
* of<Person>(
* { age: 4, name: 'Foo'},
* { age: 7, name: 'Bar'},
* { age: 5, name: 'Foo'},
* { age: 6, name: 'Foo'},
* ).pipe(
* distinctUntilChanged((p: Person, q: Person) => p.name === q.name),
* )
* .subscribe(x => console.log(x));
*
* // displays:
* // { age: 4, name: 'Foo' }
* // { age: 7, name: 'Bar' }
* // { age: 5, name: 'Foo' }
* ```
*
* @see {@link distinct}
* @see {@link distinctUntilKeyChanged}
*
* @param {function} [compare] Optional comparison function called to test if an item is distinct from the previous item in the source.
* @return {Observable} An Observable that emits items from the source Observable with distinct values.
* @method distinctUntilChanged
* @owner Observable
*/
function distinctUntilChanged(compare, keySelector) {
return function (source) { return source.lift(new DistinctUntilChangedOperator(compare, keySelector)); };
}
exports.distinctUntilChanged = distinctUntilChanged;
var DistinctUntilChangedOperator = /** @class */ (function () {
function DistinctUntilChangedOperator(compare, keySelector) {
this.compare = compare;
this.keySelector = keySelector;
}
DistinctUntilChangedOperator.prototype.call = function (subscriber, source) {
return source.subscribe(new DistinctUntilChangedSubscriber(subscriber, this.compare, this.keySelector));
};
return DistinctUntilChangedOperator;
}());
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
var DistinctUntilChangedSubscriber = /** @class */ (function (_super) {
__extends(DistinctUntilChangedSubscriber, _super);
function DistinctUntilChangedSubscriber(destination, compare, keySelector) {
var _this = _super.call(this, destination) || this;
_this.keySelector = keySelector;
_this.hasKey = false;
if (typeof compare === 'function') {
_this.compare = compare;
}
return _this;
}
DistinctUntilChangedSubscriber.prototype.compare = function (x, y) {
return x === y;
};
DistinctUntilChangedSubscriber.prototype._next = function (value) {
var key;
try {
var keySelector = this.keySelector;
key = keySelector ? keySelector(value) : value;
}
catch (err) {
return this.destination.error(err);
}
var result = false;
if (this.hasKey) {
try {
var compare = this.compare;
result = compare(this.key, key);
}
catch (err) {
return this.destination.error(err);
}
}
else {
this.hasKey = true;
}
if (!result) {
this.key = key;
this.destination.next(value);
}
};
return DistinctUntilChangedSubscriber;
}(Subscriber_1.Subscriber));
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