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node_modules/rxjs/_esm2015/operators/distinct.js

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+import { OuterSubscriber } from '../OuterSubscriber';
+import { subscribeToResult } from '../util/subscribeToResult';
+import { Set } from '../util/Set';
+/**
+ * Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from previous items.
+ *
+ * If a keySelector function is provided, then it will project each value from the source observable into a new value that it will
+ * check for equality with previously projected values. If a keySelector function is not provided, it will use each value from the
+ * source observable directly with an equality check against previous values.
+ *
+ * In JavaScript runtimes that support `Set`, this operator will use a `Set` to improve performance of the distinct value checking.
+ *
+ * In other runtimes, this operator will use a minimal implementation of `Set` that relies on an `Array` and `indexOf` under the
+ * hood, so performance will degrade as more values are checked for distinction. Even in newer browsers, a long-running `distinct`
+ * use might result in memory leaks. To help alleviate this in some scenarios, an optional `flushes` parameter is also provided so
+ * that the internal `Set` can be "flushed", basically clearing it of values.
+ *
+ * @example <caption>A simple example with numbers</caption>
+ * Observable.of(1, 1, 2, 2, 2, 1, 2, 3, 4, 3, 2, 1)
+ *   .distinct()
+ *   .subscribe(x => console.log(x)); // 1, 2, 3, 4
+ *
+ * @example <caption>An example using a keySelector function</caption>
+ * interface Person {
+ *    age: number,
+ *    name: string
+ * }
+ *
+ * Observable.of<Person>(
+ *     { age: 4, name: 'Foo'},
+ *     { age: 7, name: 'Bar'},
+ *     { age: 5, name: 'Foo'})
+ *     .distinct((p: Person) => p.name)
+ *     .subscribe(x => console.log(x));
+ *
+ * // displays:
+ * // { age: 4, name: 'Foo' }
+ * // { age: 7, name: 'Bar' }
+ *
+ * @see {@link distinctUntilChanged}
+ * @see {@link distinctUntilKeyChanged}
+ *
+ * @param {function} [keySelector] Optional function to select which value you want to check as distinct.
+ * @param {Observable} [flushes] Optional Observable for flushing the internal HashSet of the operator.
+ * @return {Observable} An Observable that emits items from the source Observable with distinct values.
+ * @method distinct
+ * @owner Observable
+ */
+export function distinct(keySelector, flushes) {
+    return (source) => source.lift(new DistinctOperator(keySelector, flushes));
+}
+class DistinctOperator {
+    constructor(keySelector, flushes) {
+        this.keySelector = keySelector;
+        this.flushes = flushes;
+    }
+    call(subscriber, source) {
+        return source.subscribe(new DistinctSubscriber(subscriber, this.keySelector, this.flushes));
+    }
+}
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+export class DistinctSubscriber extends OuterSubscriber {
+    constructor(destination, keySelector, flushes) {
+        super(destination);
+        this.keySelector = keySelector;
+        this.values = new Set();
+        if (flushes) {
+            this.add(subscribeToResult(this, flushes));
+        }
+    }
+    notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
+        this.values.clear();
+    }
+    notifyError(error, innerSub) {
+        this._error(error);
+    }
+    _next(value) {
+        if (this.keySelector) {
+            this._useKeySelector(value);
+        }
+        else {
+            this._finalizeNext(value, value);
+        }
+    }
+    _useKeySelector(value) {
+        let key;
+        const { destination } = this;
+        try {
+            key = this.keySelector(value);
+        }
+        catch (err) {
+            destination.error(err);
+            return;
+        }
+        this._finalizeNext(key, value);
+    }
+    _finalizeNext(key, value) {
+        const { values } = this;
+        if (!values.has(key)) {
+            values.add(key);
+            this.destination.next(value);
+        }
+    }
+}
+//# sourceMappingURL=distinct.js.map