Why would I use RxJS interval() or timer() polling instead of window.setInterval()?

问题

Use case: Call a function every minute (60000 ms) that dispatches store action to fetch lastUpdated status of items, which upon response and filtering, updates the store, and updated store is read as an observable and displayed in the view). This needs to happen for as long as the web app is open (so indefinitely).

Currently, I'm using this:

this.refreshDate = window.setInterval(
  () => this.store.dispatch(new FetchLastUpdate())
, 60000);

And when view is destroyed/dismounted, I delete the interval as so:

if (this.refreshDate) {
  clearInterval(this.refreshDate);
}

Is this efficient/effective, or is it troublesome?

Why would I want to use an RxJS polling strategy like:

interval(60000)
  .pipe(
    startWith(0),
    switchMap(() => this.store.dispatch(new FetchLastUpdate()))
   );

timer(0, 60000)
  .pipe(
    switchMap(() => this.store.dispatch(new FetchLastUpdate()))
  );

TL;DR: window.setInterval() vs. RxJS timer()/interval()

Conclusion/answers (for ease of research):

There is great benefit to using RxJS functions to set an interval or perform polling, these benefits are explained in the selected answer but also in comments, but it is concluded (by discussions in the comments) that for the very simple requirement defined in the "Use case" section at the beginning of this post, it is unnecessary to use RxJS, and in fact if you are not using RxJS in any other part of your program, do not import it just for this, however in my case, I had already imported and used RxJS elsewhere.

回答1:

Advantage of RxJS:

Laziness

You can create your Observables and until you call subscribe nothing is happening. Observable = pure function. This gives you more control, easier reasoning and allows for next point...

Composability

You can combine interval/timer with other operators creating custom logic very easily in unified way - for example you can map, repeat, retry, take... etc. see all operators

Error Handling

In case of an error you are responsible for calling clearTimeout/clearInterval - Observables are handling this for you. Resulting in cleaner code and fewer memory leak bugs.

Of course anything you do with Observables you can also do without Observables - but that's not the point. Observables are here to make your life easier.

Also note that interval/timer are not good observable factories for polling because they do not "wait" for your async action to finish (you can end up with multiple async calls running over each other). For that I tend to use defer and repeatWhen like this:

defer(() => doAsyncAction())
  .pipe(
    repeatWhen(notifications => notifications.pipe(delay(1234)))
  );

回答2:

window.setInterval doesn't care about your callbacks state, it'll execute at the given interval despite the status of the past callbacks execution, and the only way to make it stop and skip is clear the interval or reinitialize it.

On the other hand, RxJS Observable based solutions(interval, timer) allow you pipe conditional operators (takeWhile, skipWhile for example) which allows you to add a stop or implement a stop-start logic by just flipping a boolean flag, instead of adding complicated logic of clearing the interval, and then recreating it.

And they are observables, you can listen to them all across the application, and attach any number of listeners to it.

Error Handling is better too, you subscribe to all successes, and handle everything in a catch callback.

来源：https://stackoverflow.com/questions/52018881/why-would-i-use-rxjs-interval-or-timer-polling-instead-of-window-setinterval

标签

javascript

typescript

rxjs

rxjs5

rxjs6