# Visit time

## Visit time

| callbag                                                                                                                              | most                                                                                                                              | RxJS                                                                                                                              | xstream                                                                                                                              |
| ------------------------------------------------------------------------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ |
| [`code`](https://git.io/fAZXb) [`live`](https://codesandbox.io/s/github/fanduel-oss/refract/tree/master/examples/visit-time/callbag) | [`code`](https://git.io/fAZ1e) [`live`](https://codesandbox.io/s/github/fanduel-oss/refract/tree/master/examples/visit-time/most) | [`code`](https://git.io/fAZ1U) [`live`](https://codesandbox.io/s/github/fanduel-oss/refract/tree/master/examples/visit-time/rxjs) | [`code`](https://git.io/fAZ1I) [`live`](https://codesandbox.io/s/github/fanduel-oss/refract/tree/master/examples/visit-time/xstream) |

This examples renders a stopwatch counting the time a user spends on a page while being online.

### Aperture

Two sources observed:

* The visibility status of the page (See [page visibility API](https://developer.mozilla.org/en-US/docs/Web/API/Page_Visibility_API))
* The online status of the navigator (See [online and offline events](https://developer.mozilla.org/en-US/docs/Web/API/NavigatorOnLine/Online_and_offline_events))

Every time the page becomes visible and online, the stopwatch resumes. If the page becomes either offline or hidden, the stopwatch pauses.

### Handler

The Refract `handler` handles `pause`, `resume` and `tick` effects to track the total time spent on the page and set it in state. It handles `Date.now()` impure calls.

### Result

The end result is a stopwatch counting the number of milliseconds spent on the page when visible and online. To play with it you can:

* switch between tabs, and you'll notice the counter hasn't moved while the example tab was hidden
* toggle your navigator online status (can be done via devtools)


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