使用如下的代码监控getProduct可能返回的null值：import { Component, OnInit } from '@angular/core';

import { ActiveCartService, Product } from '@spartacus/core';

import { CurrentProductService } from '@spartacus/storefront';

import { Observable, OperatorFunction } from 'rxjs';

import { filter, map } from 'rxjs/operators';

@Component({

 selector: 'app-mycom',

 templateUrl: './mycom.component.html',

 styleUrls: ['./mycom.component.scss']

})

export class MycomComponent implements OnInit {

 jerryfilter: OperatorFunction =

   filter(this.jerrytest2);

 product$: Observable = this.currentProductService.getProduct().pipe(this.jerryfilter);

 productName$ = this.product$.pipe(map(product => product.name));

 jerrytest2(product: Product): boolean {

   const result = !!product;

   if (result === false) {

     console.log('false!');

   }

   return result;

 }

 constructor(private currentProductService: CurrentProductService, private cartService: ActiveCartService

 ) {

 }

 ngOnInit(): void {

   this.product$.subscribe(product => console.log(product));

 }

}TypeScript语句jerryfilter: OperatorFunction =

filter(this.jerrytest2);

对应的JavaScript函数：jerryfilter的JavaScript实现是一个名字叫filter的function，接收一个predicate function作为输入参数，返回一个新的函数，总金额和新的函数会基于传进来的predicate新建一个filterOperator实例：export function filter(predicate, thisArg) {

   return function filterOperatorFunction(source) {

       return source.lift(new FilterOperator(predicate, thisArg));

   };product$: Observable = this.currentProductService.getProduct().pipe(this.jerryfilter);

注意，product$是一个Observable对象，不是实际的product值：

operator指向了我传入的filter.

product$也是Observable，因此可以继续调用pipe.返回为false的情况：filter的实现，如果箭头函数返回false，就不往下继续执行了：