如何在特定时间使用 rxjs 发出请求？

Question

I need to make request three times a day at a certain time (8 AM, 12 AM, 4 PM). What is the best way to implement this?

Answer 1

This feels a bit like a strange requirement for a JS task and I think you should rather look into making a Cron task for that. But for the sake of example, here's how you can do it:

import { of, Observable, timer, EMPTY } from "rxjs";
import { map, filter, timestamp, switchMap } from "rxjs/operators";

type Hour = number;
type Minutes = number;

const atTimes = (times: [Hour, Minutes][]): Observable<[Hour, Minutes]> =>
  timer(0, 1000 * 60).pipe(
    switchMap(() => {
      const date: Date = new Date();
      const [currentHour, currentMinutes] = [
        date.getHours(),
        date.getMinutes()
      ];

      const time = times.find(
        ([hour, minutes]) => hour === currentHour && minutes === currentMinutes
      );

      if (!time) {
        return EMPTY;
      }

      return of(time);
    })
  );


atTimes([[11,48]]).subscribe(x => console.log(x));

Live demo: https://stackblitz.com/edit/rxjs-sxxe41

PS: I've assumed that the update doesn't need to be triggered as soon as the new minute starts. If that's the case, then timer should tick every second and you should use distinctUntilChanged on the current hour/minutes to wait until they're differents.

Answer 2

You should look into asyncScheduler from RxJS which uses setInterval for time based operations.

Refer to this link: https://rxjs-dev.firebaseapp.com/guide/scheduler

Ideally cron jobs are best on the server side to deal with functions need executing at different times, might be worth looking in that as well.