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- import { identity } from '../util/identity';
- import { operate } from '../util/lift';
- import { createOperatorSubscriber } from './OperatorSubscriber';
- export function distinctUntilChanged(comparator, keySelector = identity) {
- comparator = comparator !== null && comparator !== void 0 ? comparator : defaultCompare;
- return operate((source, subscriber) => {
- let previousKey;
- let first = true;
- source.subscribe(createOperatorSubscriber(subscriber, (value) => {
- const currentKey = keySelector(value);
- if (first || !comparator(previousKey, currentKey)) {
- first = false;
- previousKey = currentKey;
- subscriber.next(value);
- }
- }));
- });
- }
- function defaultCompare(a, b) {
- return a === b;
- }
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