Angular 8 Http多个调用或流

import { Component } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { forkJoin, Observable } from 'rxjs';

@Component({
  selector: 'app-example',
  template: `
    <button (click)="getData()">Get Data</button>
    <div *ngFor="let result of results$ | async">
      {{ result | json }}
    </div>
  `,
})
export class ExampleComponent {
  results$: Observable<any[]>;

  constructor(private http: HttpClient) {}

  getData() {
    const request1$ = this.http.get('https://api.example.com/data1');
    const request2$ = this.http.get('https://api.example.com/data2');
    const request3$ = this.http.get('https://api.example.com/data3');

    this.results$ = forkJoin([request1$, request2$, request3$]);
  }
}