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node_modules/rxjs/_esm2015/operators/defaultIfEmpty.js

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+import { Subscriber } from '../Subscriber';
+/* tslint:enable:max-line-length */
+/**
+ * Emits a given value if the source Observable completes without emitting any
+ * `next` value, otherwise mirrors the source Observable.
+ *
+ * <span class="informal">If the source Observable turns out to be empty, then
+ * this operator will emit a default value.</span>
+ *
+ * <img src="./img/defaultIfEmpty.png" width="100%">
+ *
+ * `defaultIfEmpty` emits the values emitted by the source Observable or a
+ * specified default value if the source Observable is empty (completes without
+ * having emitted any `next` value).
+ *
+ * @example <caption>If no clicks happen in 5 seconds, then emit "no clicks"</caption>
+ * var clicks = Rx.Observable.fromEvent(document, 'click');
+ * var clicksBeforeFive = clicks.takeUntil(Rx.Observable.interval(5000));
+ * var result = clicksBeforeFive.defaultIfEmpty('no clicks');
+ * result.subscribe(x => console.log(x));
+ *
+ * @see {@link empty}
+ * @see {@link last}
+ *
+ * @param {any} [defaultValue=null] The default value used if the source
+ * Observable is empty.
+ * @return {Observable} An Observable that emits either the specified
+ * `defaultValue` if the source Observable emits no items, or the values emitted
+ * by the source Observable.
+ * @method defaultIfEmpty
+ * @owner Observable
+ */
+export function defaultIfEmpty(defaultValue = null) {
+    return (source) => source.lift(new DefaultIfEmptyOperator(defaultValue));
+}
+class DefaultIfEmptyOperator {
+    constructor(defaultValue) {
+        this.defaultValue = defaultValue;
+    }
+    call(subscriber, source) {
+        return source.subscribe(new DefaultIfEmptySubscriber(subscriber, this.defaultValue));
+    }
+}
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+class DefaultIfEmptySubscriber extends Subscriber {
+    constructor(destination, defaultValue) {
+        super(destination);
+        this.defaultValue = defaultValue;
+        this.isEmpty = true;
+    }
+    _next(value) {
+        this.isEmpty = false;
+        this.destination.next(value);
+    }
+    _complete() {
+        if (this.isEmpty) {
+            this.destination.next(this.defaultValue);
+        }
+        this.destination.complete();
+    }
+}
+//# sourceMappingURL=defaultIfEmpty.js.map