How to call several parallel function in angular?


In Angular, you can call several functions in parallel using the forkJoin function from the RxJS library. The forkJoin function accepts an array of observables and returns an observable that emits an array of the last values emitted by each input observable when all of the input observables have completed.

Here’s an example of how to call several functions in parallel using forkJoin in Angular:

import { forkJoin } from 'rxjs';

  selector: 'app-my-component',
  template: '<p>Result: {{ result }}</p>',
export class MyComponent implements OnInit {
  result: string;

  ngOnInit() {
    const function1$ = this.myService.function1();
    const function2$ = this.myService.function2();
    const function3$ = this.myService.function3();

    forkJoin([function1$, function2$, function3$]).subscribe(([result1, result2, result3]) => {
      this.result = `${result1} - ${result2} - ${result3}`;

In this example, we import the forkJoin function from RxJS and define three observables, function1$, function2$, and function3$, that represent the functions we want to call in parallel.

We then pass an array of these observables to the forkJoin function and subscribe to the resulting observable. When the observables complete, the forkJoin function emits an array containing the last values emitted by each observable, which we destructure into result1, result2, and result3.

Finally, we set the result property of the component to a string that concatenates the results of each function.

Note that forkJoin will only emit a value when all of the input observables complete. If any input observable errors, the forkJoin observable will also error and emit that error. If you need to call the functions in parallel but handle errors separately for each function, you can use the catchError operator on each observable before passing them to forkJoin.