Merge pull request #3506 from benlesh/smaller-elementAt

Fix elementAt defaultValue, make elementAt impl smaller
ReactiveX · Mar 31, 2018 · 37fcc33 · 37fcc33
2 parents 3db18d1 + 13706e7
commit 37fcc33
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Showing 2 changed files with 14 additions and 46 deletions.
diff --git a/compat/operator/elementAt.ts b/compat/operator/elementAt.ts
@@ -45,5 +45,5 @@ import { elementAt as higherOrder } from 'rxjs/operators';
  * @owner Observable
  */
 export function elementAt<T>(this: Observable<T>, index: number, defaultValue?: T): Observable<T> {
- return higherOrder(index, defaultValue)(this);
+ return higherOrder.apply(undefined, arguments)(this);
 }
diff --git a/src/internal/operators/elementAt.ts b/src/internal/operators/elementAt.ts
@@ -3,6 +3,10 @@ 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
@@ -47,49 +51,13 @@ import { MonoTypeOperatorFunction, TeardownLogic } from '../types';
  * @owner Observable
  */
 export function elementAt<T>(index: number, defaultValue?: T): MonoTypeOperatorFunction<T> {
- return (source: Observable<T>) => source.lift(new ElementAtOperator(index, defaultValue));
-}
-
-class ElementAtOperator<T> implements Operator<T, T> {
-
- constructor(private index: number, private defaultValue?: T) {
- if (index < 0) {
- throw new ArgumentOutOfRangeError;
- }
- }
-
- call(subscriber: Subscriber<T>, source: any): TeardownLogic {
- return source.subscribe(new ElementAtSubscriber(subscriber, this.index, this.defaultValue));
- }
-}
-
-/**
- * We need this JSDoc comment for affecting ESDoc.
- * @ignore
- * @extends {Ignored}
- */
-class ElementAtSubscriber<T> extends Subscriber<T> {
-
- constructor(destination: Subscriber<T>, private index: number, private defaultValue?: T) {
- super(destination);
- }
-
- protected _next(x: T) {
- if (this.index-- === 0) {
- this.destination.next(x);
- this.destination.complete();
- }
- }
-
- protected _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();
- }
+ 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()),
+ );
 }