es6/operator/windowCount.js

import { Subscriber } from '../Subscriber';
import { Subject } from '../Subject';
/**
 * 将源 Observable 的值分支成多个嵌套的 Observable ，每个嵌套的 Observable 最多发出 windowSize 个值。
 *
 * <span class="informal">就像是 {@link bufferCount}, 但是返回嵌套的 Observable 而不是数组。</span>
 *
 * <img src="./img/windowCount.png" width="100%">

 * 返回的 Observable 发出从源 Observable 收集到的项的窗口。
 * 输出 Observable 每M(M = startWindowEvery)个项发出新窗口，每个窗口包含的项数不得超过N个(N = windowSize)。
 * 当源 Observable 完成或者遇到错误,输出 Observable 发出当前窗口并且传播从源 Observable 收到的通知。
 * 如果没有提供 startWindowEvery ，那么在源 Observable 的起始处立即开启新窗口，并且当每个窗口的大小达到 windowSize 时完成。
 *
 * @example <caption>从第一个点击事件开始，忽略第3N次点击</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var result = clicks.windowCount(3)
 *   .map(win => win.skip(1)) // 跳过每三个点击中的第一个
 *   .mergeAll(); // 打平高阶 Observable
 * result.subscribe(x => console.log(x));
 *
 * @example <caption>从第三个点击事件开始，忽略第3N次点击</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var result = clicks.windowCount(2, 3)
 *   .mergeAll(); // 打平高阶 Observable
 * result.subscribe(x => console.log(x));
 *
 * @see {@link window}
 * @see {@link windowTime}
 * @see {@link windowToggle}
 * @see {@link windowWhen}
 * @see {@link bufferCount}
 *
 * @param {number} windowSize 每个窗口最多可以发送的个数。
 * @param {number} [startWindowEvery] 开启新窗口的间隔。
 * 比如，如果 `startWindowEvery` 是 `2`, 新窗口会在源中每个第二个值开启。默认情况下，新窗口是在源 Observable 的起始处开启的。
 * @return {Observable<Observable<T>>} 窗口的 Observable，每个窗口又是值的 Observable 。(译者注：其实就是高阶 Observable )
 * @method windowCount
 * @owner Observable
 */
export function windowCount(windowSize, startWindowEvery = 0) {
    return this.lift(new WindowCountOperator(windowSize, startWindowEvery));
}
class WindowCountOperator {
    constructor(windowSize, startWindowEvery) {
        this.windowSize = windowSize;
        this.startWindowEvery = startWindowEvery;
    }
    call(subscriber, source) {
        return source.subscribe(new WindowCountSubscriber(subscriber, this.windowSize, this.startWindowEvery));
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class WindowCountSubscriber extends Subscriber {
    constructor(destination, windowSize, startWindowEvery) {
        super(destination);
        this.destination = destination;
        this.windowSize = windowSize;
        this.startWindowEvery = startWindowEvery;
        this.windows = [new Subject()];
        this.count = 0;
        destination.next(this.windows[0]);
    }
    _next(value) {
        const startWindowEvery = (this.startWindowEvery > 0) ? this.startWindowEvery : this.windowSize;
        const destination = this.destination;
        const windowSize = this.windowSize;
        const windows = this.windows;
        const len = windows.length;
        for (let i = 0; i < len && !this.closed; i++) {
            windows[i].next(value);
        }
        const c = this.count - windowSize + 1;
        if (c >= 0 && c % startWindowEvery === 0 && !this.closed) {
            windows.shift().complete();
        }
        if (++this.count % startWindowEvery === 0 && !this.closed) {
            const window = new Subject();
            windows.push(window);
            destination.next(window);
        }
    }
    _error(err) {
        const windows = this.windows;
        if (windows) {
            while (windows.length > 0 && !this.closed) {
                windows.shift().error(err);
            }
        }
        this.destination.error(err);
    }
    _complete() {
        const windows = this.windows;
        if (windows) {
            while (windows.length > 0 && !this.closed) {
                windows.shift().complete();
            }
        }
        this.destination.complete();
    }
    _unsubscribe() {
        this.count = 0;
        this.windows = null;
    }
}
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