如何在subscribe方法中只发出最后一个请求

import { fromEvent } from 'rxjs';
import { debounceTime } from 'rxjs/operators';

const button = document.getElementById('button');
const input = document.getElementById('input');

const click$ = fromEvent(button, 'click');

click$
  .pipe(debounceTime(300))
  .subscribe(() => {
    // 发出最后一个请求的逻辑
    const value = input.value;
    console.log(`发送请求：${value}`);
  });

import { fromEvent } from 'rxjs';
import { switchMap } from 'rxjs/operators';

const button = document.getElementById('button');
const input = document.getElementById('input');

const click$ = fromEvent(button, 'click');

click$
  .pipe(
    switchMap(() => {
      // 返回一个新的Observable对象，代表最后一个请求
      const value = input.value;
      console.log(`发送请求：${value}`);
      return ajax.getJSON(`https://api.example.com/data?value=${value}`);
    })
  )
  .subscribe(response => {
    // 处理最后一个请求的响应
    console.log('请求响应：', response);
  });