Rxjs debounce 操作符在 SAP Spartacus 函数节流中的一个实际使用例子

在 window-ref.ts 的实现里，定义了一个每隔 300 毫秒，通过 fromEvent 发射一个 resize event 的Observable：

/**   * Returns an observable for the window resize event and emits an event   * every 300ms in case of resizing. An event is simulated initially.   *   * If there's no window object available (i.e. in SSR), a null value is emitted.   */  get resize$(): Observable<any> {    if (!this.nativeWindow) {      return of(null);    } else {      return fromEvent(this.nativeWindow, 'resize').pipe(        debounceTime(300),        startWith({ target: this.nativeWindow }),        distinctUntilChanged()      );    }  }

加上 distingctUntilChanged 操作符后，能过滤掉完全一致的 resize event. 下面的例子，展示了如何使用 distingctUntilChanged，将数字序列里重复的数字过滤掉。distingctUntilChanged 默认会将当前元素和前一元素做比较。

import { of } from 'rxjs';import { distinctUntilChanged } from 'rxjs/operators';of(1, 1, 2, 2, 2, 1, 1, 2, 3, 3, 4).pipe(    distinctUntilChanged(),  )  .subscribe(x => console.log(x)); // 1, 2, 1, 2, 3, 4

下列例子展示了如何将自定义的比较逻辑，通过箭头函数作为参数，传入 distinctUntilChanged 里。

import { of } from 'rxjs';import { distinctUntilChanged } from 'rxjs/operators';interface Person {   age: number,   name: string}of<Person>(    { age: 4, name: 'Foo'},    { age: 7, name: 'Bar'},    { age: 5, name: 'Foo'},    { age: 6, name: 'Foo'},  ).pipe(    distinctUntilChanged((p: Person, q: Person) => p.name === q.name),  )  .subscribe(x => console.log(x));// displays:// { age: 4, name: 'Foo' }// { age: 7, name: 'Bar' }// { age: 5, name: 'Foo' }