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node_modules/rxjs/_esm2015/operators/elementAt.js

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+import { Subscriber } from '../Subscriber';
+import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError';
+/**
+ * Emits the single value at the specified `index` in a sequence of emissions
+ * from the source Observable.
+ *
+ * <span class="informal">Emits only the i-th value, then completes.</span>
+ *
+ * <img src="./img/elementAt.png" width="100%">
+ *
+ * `elementAt` returns an Observable that emits the item at the specified
+ * `index` in the source Observable, or a default value if that `index` is out
+ * of range and the `default` argument is provided. If the `default` argument is
+ * not given and the `index` is out of range, the output Observable will emit an
+ * `ArgumentOutOfRangeError` error.
+ *
+ * @example <caption>Emit only the third click event</caption>
+ * var clicks = Rx.Observable.fromEvent(document, 'click');
+ * var result = clicks.elementAt(2);
+ * result.subscribe(x => console.log(x));
+ *
+ * // Results in:
+ * // click 1 = nothing
+ * // click 2 = nothing
+ * // click 3 = MouseEvent object logged to console
+ *
+ * @see {@link first}
+ * @see {@link last}
+ * @see {@link skip}
+ * @see {@link single}
+ * @see {@link take}
+ *
+ * @throws {ArgumentOutOfRangeError} When using `elementAt(i)`, it delivers an
+ * ArgumentOutOrRangeError to the Observer's `error` callback if `i < 0` or the
+ * Observable has completed before emitting the i-th `next` notification.
+ *
+ * @param {number} index Is the number `i` for the i-th source emission that has
+ * happened since the subscription, starting from the number `0`.
+ * @param {T} [defaultValue] The default value returned for missing indices.
+ * @return {Observable} An Observable that emits a single item, if it is found.
+ * Otherwise, will emit the default value if given. If not, then emits an error.
+ * @method elementAt
+ * @owner Observable
+ */
+export function elementAt(index, defaultValue) {
+    return (source) => source.lift(new ElementAtOperator(index, defaultValue));
+}
+class ElementAtOperator {
+    constructor(index, defaultValue) {
+        this.index = index;
+        this.defaultValue = defaultValue;
+        if (index < 0) {
+            throw new ArgumentOutOfRangeError;
+        }
+    }
+    call(subscriber, source) {
+        return source.subscribe(new ElementAtSubscriber(subscriber, this.index, this.defaultValue));
+    }
+}
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+class ElementAtSubscriber extends Subscriber {
+    constructor(destination, index, defaultValue) {
+        super(destination);
+        this.index = index;
+        this.defaultValue = defaultValue;
+    }
+    _next(x) {
+        if (this.index-- === 0) {
+            this.destination.next(x);
+            this.destination.complete();
+        }
+    }
+    _complete() {
+        const destination = this.destination;
+        if (this.index >= 0) {
+            if (typeof this.defaultValue !== 'undefined') {
+                destination.next(this.defaultValue);
+            }
+            else {
+                destination.error(new ArgumentOutOfRangeError);
+            }
+        }
+        destination.complete();
+    }
+}
+//# sourceMappingURL=elementAt.js.map