biofriction-wp-theme/node_modules/rxjs/_esm2015/operators/distinctUntilChanged.js

98 lines
3.2 KiB
JavaScript

import { Subscriber } from '../Subscriber';
import { tryCatch } from '../util/tryCatch';
import { errorObject } from '../util/errorObject';
/* 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 <caption>A simple example with numbers</caption>
* Observable.of(1, 1, 2, 2, 2, 1, 1, 2, 3, 3, 4)
* .distinctUntilChanged()
* .subscribe(x => console.log(x)); // 1, 2, 1, 2, 3, 4
*
* @example <caption>An example using a compare function</caption>
* interface Person {
* age: number,
* name: string
* }
*
* Observable.of<Person>(
* { age: 4, name: 'Foo'},
* { age: 7, name: 'Bar'},
* { age: 5, name: 'Foo'})
* { age: 6, name: 'Foo'})
* .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
*/
export function distinctUntilChanged(compare, keySelector) {
return (source) => source.lift(new DistinctUntilChangedOperator(compare, keySelector));
}
class DistinctUntilChangedOperator {
constructor(compare, keySelector) {
this.compare = compare;
this.keySelector = keySelector;
}
call(subscriber, source) {
return source.subscribe(new DistinctUntilChangedSubscriber(subscriber, this.compare, this.keySelector));
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
class DistinctUntilChangedSubscriber extends Subscriber {
constructor(destination, compare, keySelector) {
super(destination);
this.keySelector = keySelector;
this.hasKey = false;
if (typeof compare === 'function') {
this.compare = compare;
}
}
compare(x, y) {
return x === y;
}
_next(value) {
const keySelector = this.keySelector;
let key = value;
if (keySelector) {
key = tryCatch(this.keySelector)(value);
if (key === errorObject) {
return this.destination.error(errorObject.e);
}
}
let result = false;
if (this.hasKey) {
result = tryCatch(this.compare)(this.key, key);
if (result === errorObject) {
return this.destination.error(errorObject.e);
}
}
else {
this.hasKey = true;
}
if (Boolean(result) === false) {
this.key = key;
this.destination.next(value);
}
}
}
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