48 lines
2.3 KiB
TypeScript
48 lines
2.3 KiB
TypeScript
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import { Observable } from '../Observable';
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/**
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* Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from previous items.
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*
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* If a keySelector function is provided, then it will project each value from the source observable into a new value that it will
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* check for equality with previously projected values. If a keySelector function is not provided, it will use each value from the
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* source observable directly with an equality check against previous values.
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*
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* In JavaScript runtimes that support `Set`, this operator will use a `Set` to improve performance of the distinct value checking.
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*
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* In other runtimes, this operator will use a minimal implementation of `Set` that relies on an `Array` and `indexOf` under the
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* hood, so performance will degrade as more values are checked for distinction. Even in newer browsers, a long-running `distinct`
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* use might result in memory leaks. To help alleviate this in some scenarios, an optional `flushes` parameter is also provided so
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* that the internal `Set` can be "flushed", basically clearing it of values.
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*
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* @example <caption>A simple example with numbers</caption>
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* Observable.of(1, 1, 2, 2, 2, 1, 2, 3, 4, 3, 2, 1)
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* .distinct()
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* .subscribe(x => console.log(x)); // 1, 2, 3, 4
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*
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* @example <caption>An example using a keySelector function</caption>
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* interface Person {
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* age: number,
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* name: string
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* }
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*
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* Observable.of<Person>(
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* { age: 4, name: 'Foo'},
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* { age: 7, name: 'Bar'},
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* { age: 5, name: 'Foo'})
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* .distinct((p: Person) => p.name)
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* .subscribe(x => console.log(x));
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*
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* // displays:
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* // { age: 4, name: 'Foo' }
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* // { age: 7, name: 'Bar' }
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*
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* @see {@link distinctUntilChanged}
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* @see {@link distinctUntilKeyChanged}
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*
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* @param {function} [keySelector] Optional function to select which value you want to check as distinct.
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* @param {Observable} [flushes] Optional Observable for flushing the internal HashSet of the operator.
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* @return {Observable} An Observable that emits items from the source Observable with distinct values.
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* @method distinct
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* @owner Observable
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*/
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export declare function distinct<T, K>(this: Observable<T>, keySelector?: (value: T) => K, flushes?: Observable<any>): Observable<T>;
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