Fix EsLint Brackets (error markup 'const').

node_modules/rxjs/src/internal/operators/elementAt.ts

@@ -0,0 +1,66 @@
+import { Operator } from '../Operator';
+import { Subscriber } from '../Subscriber';
+import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError';
+import { Observable } from '../Observable';
+import { MonoTypeOperatorFunction, TeardownLogic } from '../types';
+import { filter } from './filter';
+import { throwIfEmpty } from './throwIfEmpty';
+import { defaultIfEmpty } from './defaultIfEmpty';
+import { take } from './take';
+
+/**
+ * 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>
+ *
+ * ![](elementAt.png)
+ *
+ * `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
+ * Emit only the third click event
+ * ```javascript
+ * const clicks = fromEvent(document, 'click');
+ * const result = clicks.pipe(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<T>(index: number, defaultValue?: T): MonoTypeOperatorFunction<T> {
+  if (index < 0) { throw new ArgumentOutOfRangeError(); }
+  const hasDefaultValue = arguments.length >= 2;
+  return (source: Observable<T>) => source.pipe(
+    filter((v, i) => i === index),
+    take(1),
+    hasDefaultValue
+      ? defaultIfEmpty(defaultValue)
+      : throwIfEmpty(() => new ArgumentOutOfRangeError()),
+  );
+}