feat(bufferCount): add higher-order lettable version of bufferCount

src/operator/bufferCount.ts

@@ -1,7 +1,6 @@
-import { Operator } from '../Operator';
-import { Subscriber } from '../Subscriber';
+
 import { Observable } from '../Observable';
-import { TeardownLogic } from '../Subscription';
+import { bufferCount as higherOrder } from '../operators';
 
 /**
  * Buffers the source Observable values until the size hits the maximum
@@ -45,98 +44,5 @@ import { TeardownLogic } from '../Subscription';
  * @owner Observable
  */
 export function bufferCount<T>(this: Observable<T>, bufferSize: number, startBufferEvery: number = null): Observable<T[]> {
-  return this.lift(new BufferCountOperator<T>(bufferSize, startBufferEvery));
-}
-
-class BufferCountOperator<T> implements Operator<T, T[]> {
-  private subscriberClass: any;
-
-  constructor(private bufferSize: number, private startBufferEvery: number) {
-    if (!startBufferEvery || bufferSize === startBufferEvery) {
-      this.subscriberClass = BufferCountSubscriber;
-    } else {
-      this.subscriberClass = BufferSkipCountSubscriber;
-    }
-  }
-
-  call(subscriber: Subscriber<T[]>, source: any): TeardownLogic {
-    return source.subscribe(new this.subscriberClass(subscriber, this.bufferSize, this.startBufferEvery));
-  }
-}
-
-/**
- * We need this JSDoc comment for affecting ESDoc.
- * @ignore
- * @extends {Ignored}
- */
-class BufferCountSubscriber<T> extends Subscriber<T> {
-  private buffer: T[] = [];
-
-  constructor(destination: Subscriber<T[]>, private bufferSize: number) {
-    super(destination);
-  }
-
-  protected _next(value: T): void {
-    const buffer = this.buffer;
-
-    buffer.push(value);
-
-    if (buffer.length == this.bufferSize) {
-      this.destination.next(buffer);
-      this.buffer = [];
-    }
-  }
-
-  protected _complete(): void {
-    const buffer = this.buffer;
-    if (buffer.length > 0) {
-      this.destination.next(buffer);
-    }
-    super._complete();
-  }
-}
-
-/**
- * We need this JSDoc comment for affecting ESDoc.
- * @ignore
- * @extends {Ignored}
- */
-class BufferSkipCountSubscriber<T> extends Subscriber<T> {
-  private buffers: Array<T[]> = [];
-  private count: number = 0;
-
-  constructor(destination: Subscriber<T[]>, private bufferSize: number, private startBufferEvery: number) {
-    super(destination);
-  }
-
-  protected _next(value: T): void {
-    const { bufferSize, startBufferEvery, buffers, count } = this;
-
-    this.count++;
-    if (count % startBufferEvery === 0) {
-      buffers.push([]);
-    }
-
-    for (let i = buffers.length; i--; ) {
-      const buffer = buffers[i];
-      buffer.push(value);
-      if (buffer.length === bufferSize) {
-        buffers.splice(i, 1);
-        this.destination.next(buffer);
-      }
-    }
-  }
-
-  protected _complete(): void {
-    const { buffers, destination } = this;
-
-    while (buffers.length > 0) {
-      let buffer = buffers.shift();
-      if (buffer.length > 0) {
-        destination.next(buffer);
-      }
-    }
-    super._complete();
-  }
-
+  return higherOrder(bufferSize, startBufferEvery)(this);
 }

src/operators/bufferCount.ts

@@ -0,0 +1,145 @@
+import { Operator } from '../Operator';
+import { Subscriber } from '../Subscriber';
+import { Observable } from '../Observable';
+import { TeardownLogic } from '../Subscription';
+import { OperatorFunction } from '../interfaces';
+
+/**
+ * Buffers the source Observable values until the size hits the maximum
+ * `bufferSize` given.
+ *
+ * <span class="informal">Collects values from the past as an array, and emits
+ * that array only when its size reaches `bufferSize`.</span>
+ *
+ * <img src="./img/bufferCount.png" width="100%">
+ *
+ * Buffers a number of values from the source Observable by `bufferSize` then
+ * emits the buffer and clears it, and starts a new buffer each
+ * `startBufferEvery` values. If `startBufferEvery` is not provided or is
+ * `null`, then new buffers are started immediately at the start of the source
+ * and when each buffer closes and is emitted.
+ *
+ * @example <caption>Emit the last two click events as an array</caption>
+ * var clicks = Rx.Observable.fromEvent(document, 'click');
+ * var buffered = clicks.bufferCount(2);
+ * buffered.subscribe(x => console.log(x));
+ *
+ * @example <caption>On every click, emit the last two click events as an array</caption>
+ * var clicks = Rx.Observable.fromEvent(document, 'click');
+ * var buffered = clicks.bufferCount(2, 1);
+ * buffered.subscribe(x => console.log(x));
+ *
+ * @see {@link buffer}
+ * @see {@link bufferTime}
+ * @see {@link bufferToggle}
+ * @see {@link bufferWhen}
+ * @see {@link pairwise}
+ * @see {@link windowCount}
+ *
+ * @param {number} bufferSize The maximum size of the buffer emitted.
+ * @param {number} [startBufferEvery] Interval at which to start a new buffer.
+ * For example if `startBufferEvery` is `2`, then a new buffer will be started
+ * on every other value from the source. A new buffer is started at the
+ * beginning of the source by default.
+ * @return {Observable<T[]>} An Observable of arrays of buffered values.
+ * @method bufferCount
+ * @owner Observable
+ */
+export function bufferCount<T>(bufferSize: number, startBufferEvery: number = null): OperatorFunction<T, T[]> {
+  return function bufferCountOperatorFunction(source: Observable<T>) {
+    return source.lift(new BufferCountOperator<T>(bufferSize, startBufferEvery));
+  };
+}
+
+class BufferCountOperator<T> implements Operator<T, T[]> {
+  private subscriberClass: any;
+
+  constructor(private bufferSize: number, private startBufferEvery: number) {
+    if (!startBufferEvery || bufferSize === startBufferEvery) {
+      this.subscriberClass = BufferCountSubscriber;
+    } else {
+      this.subscriberClass = BufferSkipCountSubscriber;
+    }
+  }
+
+  call(subscriber: Subscriber<T[]>, source: any): TeardownLogic {
+    return source.subscribe(new this.subscriberClass(subscriber, this.bufferSize, this.startBufferEvery));
+  }
+}
+
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+class BufferCountSubscriber<T> extends Subscriber<T> {
+  private buffer: T[] = [];
+
+  constructor(destination: Subscriber<T[]>, private bufferSize: number) {
+    super(destination);
+  }
+
+  protected _next(value: T): void {
+    const buffer = this.buffer;
+
+    buffer.push(value);
+
+    if (buffer.length == this.bufferSize) {
+      this.destination.next(buffer);
+      this.buffer = [];
+    }
+  }
+
+  protected _complete(): void {
+    const buffer = this.buffer;
+    if (buffer.length > 0) {
+      this.destination.next(buffer);
+    }
+    super._complete();
+  }
+}
+
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+class BufferSkipCountSubscriber<T> extends Subscriber<T> {
+  private buffers: Array<T[]> = [];
+  private count: number = 0;
+
+  constructor(destination: Subscriber<T[]>, private bufferSize: number, private startBufferEvery: number) {
+    super(destination);
+  }
+
+  protected _next(value: T): void {
+    const { bufferSize, startBufferEvery, buffers, count } = this;
+
+    this.count++;
+    if (count % startBufferEvery === 0) {
+      buffers.push([]);
+    }
+
+    for (let i = buffers.length; i--; ) {
+      const buffer = buffers[i];
+      buffer.push(value);
+      if (buffer.length === bufferSize) {
+        buffers.splice(i, 1);
+        this.destination.next(buffer);
+      }
+    }
+  }
+
+  protected _complete(): void {
+    const { buffers, destination } = this;
+
+    while (buffers.length > 0) {
+      let buffer = buffers.shift();
+      if (buffer.length > 0) {
+        destination.next(buffer);
+      }
+    }
+    super._complete();
+  }
+
+}

src/operators/index.ts

@@ -1,6 +1,7 @@
 export { audit } from './audit';
 export { auditTime } from './auditTime';
 export { buffer } from './buffer';
+export { bufferCount } from './bufferCount';
 export { catchError } from './catchError';
 export { concat } from './concat';
 export { concatAll } from './concatAll';