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node_modules/rxjs/_esm2015/operators/distinctUntilChanged.js

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+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);
+        }
+    }
+}
+//# sourceMappingURL=distinctUntilChanged.js.map