Angular :如何处理异步问题？

function fetchData(callback: (data: any) => void) {
  setTimeout(() => {
    const data = 'Async data';
    callback(data);
  }, 1000);
}

fetchData((data) => {
  console.log(data); // 输出：Async data
});

function fetchData(): Promise<any> {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      const data = 'Async data';
      resolve(data);
    }, 1000);
  });
}

fetchData().then((data) => {
  console.log(data); // 输出：Async data
});

async function fetchData(): Promise<any> {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      const data = 'Async data';
      resolve(data);
    }, 1000);
  });
}

async function getData() {
  const data = await fetchData();
  console.log(data); // 输出：Async data
}

getData();

import { Observable } from 'rxjs';

function fetchData(): Observable<any> {
  return new Observable((observer) => {
    setTimeout(() => {
      const data = 'Async data';
      observer.next(data);
      observer.complete();
    }, 1000);
  });
}

fetchData().subscribe((data) => {
  console.log(data); // 输出：Async data
});