feat(throttle): add throttle operator with durationSelector

Add new throttle operator (previous throttle was renamed to throttleTime) that takes a
durationSelector parameter, much like debounce does.

Resolves ReactiveX#496.

src/CoreOperators.ts

@@ -75,6 +75,7 @@ export interface CoreOperators<T> {
  switchMapTo?: <R>(observable: Observable<any>, projectResult?: (x: T, y: any, ix: number, iy: number) => R) => Observable<R>;
  take?: (count: number) => Observable<T>;
  takeUntil?: (notifier: Observable<any>) => Observable<T>;
+ throttle?: (durationSelector: (value: T) => Observable<any> | Promise<any>) => Observable<T>;
  throttleTime?: (delay: number, scheduler?: Scheduler) => Observable<T>;
  timeout?: (due: number | Date, errorToSend?: any, scheduler?: Scheduler) => Observable<T>;
  timeoutWith?: <R>(due: number | Date, withObservable: Observable<R>, scheduler?: Scheduler) => Observable<T> | Observable<R>;

src/Observable.ts

@@ -228,6 +228,7 @@ export class Observable<T> implements CoreOperators<T> {
  switchMapTo: <R>(observable: Observable<any>, projectResult?: (x: T, y: any, ix: number, iy: number) => R) => Observable<R>;
  take: (count: number) => Observable<T>;
  takeUntil: (notifier: Observable<any>) => Observable<T>;
+ throttle: (durationSelector: (value: T) => Observable<any> | Promise<any>) => Observable<T>;
  throttleTime: (delay: number, scheduler?: Scheduler) => Observable<T>;
  timeout: (due: number | Date, errorToSend?: any, scheduler?: Scheduler) => Observable<T>;
  timeoutWith: <R>(due: number | Date, withObservable: Observable<R>, scheduler?: Scheduler) => Observable<T> | Observable<R>;

src/Rx.KitchenSink.ts

@@ -285,6 +285,9 @@ observableProto.take = take;
 import {takeUntil} from './operators/takeUntil';
 observableProto.takeUntil = takeUntil;
 
+import {throttle} from './operators/throttle';
+observableProto.throttle = throttle;
+
 import {throttleTime} from './operators/throttleTime';
 observableProto.throttleTime = throttleTime;
 

src/Rx.ts

@@ -239,6 +239,9 @@ observableProto.take = take;
 import {takeUntil} from './operators/takeUntil';
 observableProto.takeUntil = takeUntil;
 
+import {throttle} from './operators/throttle';
+observableProto.throttle = throttle;
+
 import {throttleTime} from './operators/throttleTime';
 observableProto.throttleTime = throttleTime;
 

src/operators/throttle.ts

@@ -0,0 +1,84 @@
+import {Operator} from '../Operator';
+import {Observable} from '../Observable';
+import {PromiseObservable} from '../observables/PromiseObservable';
+import {Subscriber} from '../Subscriber';
+import {Subscription} from '../Subscription';
+
+import {tryCatch} from '../util/tryCatch';
+import {isPromise} from '../util/isPromise';
+import {errorObject} from '../util/errorObject';
+
+export function throttle<T>(durationSelector: (value: T) => Observable<any> | Promise<any>): Observable<T> {
+ return this.lift(new ThrottleOperator(durationSelector));
+}
+
+class ThrottleOperator<T, R> implements Operator<T, R> {
+ constructor(private durationSelector: (value: T) => Observable<any> | Promise<any>) {
+ }
+
+ call(subscriber: Subscriber<T>): Subscriber<T> {
+ return new ThrottleSubscriber(subscriber, this.durationSelector);
+ }
+}
+
+class ThrottleSubscriber<T> extends Subscriber<T> {
+ private throttled: Subscription<any>;
+
+ constructor(destination: Subscriber<T>,
+ private durationSelector: (value: T) => Observable<any> | Promise<any>) {
+ super(destination);
+ }
+
+ _next(value: T): void {
+ if (!this.throttled) {
+ const destination = this.destination;
+ let duration = tryCatch(this.durationSelector)(value);
+ if (duration === errorObject) {
+ destination.error(errorObject.e);
+ return;
+ }
+ if (isPromise(duration)) {
+ duration = PromiseObservable.create(duration);
+ }
+ this.add(this.throttled = duration._subscribe(new ThrottleDurationSelectorSubscriber(this)));
+ destination.next(value);
+ }
+ }
+
+ _error(err: any): void {
+ this.clearThrottle();
+ super._error(err);
+ }
+
+ _complete(): void {
+ this.clearThrottle();
+ super._complete();
+ }
+
+ clearThrottle(): void {
+ const throttled = this.throttled;
+ if (throttled) {
+ throttled.unsubscribe();
+ this.remove(throttled);
+ this.throttled = null;
+ }
+ }
+}
+
+class ThrottleDurationSelectorSubscriber<T> extends Subscriber<T> {
+ constructor(private parent: ThrottleSubscriber<any>) {
+ super(null);
+ }
+
+ _next(unused: T): void {
+ this.parent.clearThrottle();
+ }
+
+ _error(err): void {
+ this.parent.error(err);
+ }
+
+ _complete(): void {
+ this.parent.clearThrottle();
+ }
+}