# Dynamically Upgrade Your JS App
### Watch For a Version
- Polling
- Websockets
- Use semver
## Watch Page Visibility
```js
window.document.addEventListener('visibilitychange', () => {
if (window.document.hidden) {
window.alert('I will not be ignored!');
}
});
```
## Watch Input, Progress, State
Guarantee reconstruction
## Watch For Downtime
Are they AFK?
## Look Before You Leap
```js
if (navigator.onLine) {
console.log('online');
}
window.addEventListener('offline',
() => { console.log('offline'); });
window.addEventListener('online',
() => { console.log('online'); });
```
## Satisfied?
```
Semver Upgrade
Invisible
Idempotent State
Downtime
+ Connectivity
--------------
Reload!
```
## Reload API
```js
// reload *from the server*
window.location.reload(true);
// avoid the browser cache
```
## Good Resources
- [Page Visibility API - Mozilla](https://developer.mozilla.org/en-US/docs/Web/API/Page_Visibility_API)
- [Location.reload() - Mozilla](https://developer.mozilla.org/en-US/docs/Web/API/Location/reload)
- [Navigator.onLine - Mozilla](https://developer.mozilla.org/en-US/docs/Web/API/NavigatorOnLine/onLine)
## We're Hiring @ OfficeLuv!
https://officeluv.github.io
## Thanks!
https://www.andjosh.com/presents