98 lines
3.2 KiB
JavaScript
98 lines
3.2 KiB
JavaScript
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import { Subscriber } from '../Subscriber';
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import { tryCatch } from '../util/tryCatch';
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import { errorObject } from '../util/errorObject';
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/* tslint:enable:max-line-length */
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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 the previous item.
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*
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* 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.
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*
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* If a comparator function is not provided, an equality check is used by default.
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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, 1, 2, 3, 3, 4)
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* .distinctUntilChanged()
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* .subscribe(x => console.log(x)); // 1, 2, 1, 2, 3, 4
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*
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* @example <caption>An example using a compare 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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* { age: 6, name: 'Foo'})
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* .distinctUntilChanged((p: Person, q: Person) => p.name === q.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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* // { age: 5, name: 'Foo' }
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*
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* @see {@link distinct}
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* @see {@link distinctUntilKeyChanged}
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*
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* @param {function} [compare] Optional comparison function called to test if an item is distinct from the previous item in the source.
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* @return {Observable} An Observable that emits items from the source Observable with distinct values.
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* @method distinctUntilChanged
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* @owner Observable
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*/
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export function distinctUntilChanged(compare, keySelector) {
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return (source) => source.lift(new DistinctUntilChangedOperator(compare, keySelector));
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}
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class DistinctUntilChangedOperator {
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constructor(compare, keySelector) {
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this.compare = compare;
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this.keySelector = keySelector;
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}
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call(subscriber, source) {
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return source.subscribe(new DistinctUntilChangedSubscriber(subscriber, this.compare, this.keySelector));
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}
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}
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/**
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* We need this JSDoc comment for affecting ESDoc.
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* @ignore
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* @extends {Ignored}
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*/
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class DistinctUntilChangedSubscriber extends Subscriber {
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constructor(destination, compare, keySelector) {
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super(destination);
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this.keySelector = keySelector;
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this.hasKey = false;
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if (typeof compare === 'function') {
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this.compare = compare;
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}
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}
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compare(x, y) {
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return x === y;
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}
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_next(value) {
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const keySelector = this.keySelector;
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let key = value;
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if (keySelector) {
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key = tryCatch(this.keySelector)(value);
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if (key === errorObject) {
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return this.destination.error(errorObject.e);
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}
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}
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let result = false;
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if (this.hasKey) {
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result = tryCatch(this.compare)(this.key, key);
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if (result === errorObject) {
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return this.destination.error(errorObject.e);
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}
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}
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else {
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this.hasKey = true;
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}
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if (Boolean(result) === false) {
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this.key = key;
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this.destination.next(value);
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}
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}
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}
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//# sourceMappingURL=distinctUntilChanged.js.map
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