angular如何在每次迭代到下一个元素之前等待sucbribe响应

import { from } from 'rxjs';
import { concatMap } from 'rxjs/operators';

// 假设你有一个元素数组
const elements = [1, 2, 3, 4, 5];

// 假设这是一个返回Observable的函数
function processElement(element: number) {
  return new Promise((resolve) => {
    setTimeout(() => {
      console.log(`Processed element: ${element}`);
      resolve();
    }, 1000);
  }).then(() => from(Promise.resolve(element)));
}

// 使用from将数组转换为Observable序列
from(elements).pipe(
  concatMap((element) => processElement(element))
).subscribe({
  next: (value) => console.log(`Next value: ${value}`),
  complete: () => console.log('All elements processed')
});

import { Subject } from 'rxjs';
import { takeUntil } from 'rxjs/operators';

@Component({
  // ...
})
export class MyComponent implements OnInit, OnDestroy {
  private destroy$ = new Subject<void>();

  ngOnInit() {
    from(elements).pipe(
      concatMap((element) => processElement(element)),
      takeUntil(this.destroy$)
    ).subscribe({
      next: (value) => console.log(`Next value: ${value}`),
      complete: () => console.log('All elements processed')
    });
  }

  ngOnDestroy() {
    this.destroy$.next();
    this.destroy$.complete();
  }
}