The onoffline property of the WorkerGlobalScope interface represents an event handler to be called when the offline event occurs.
self.onoffline = function() { ... };
The following code snippet shows an onoffline handler set inside a worker:
self.onoffline = function() { console.log('Your worker is now offline'); }
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
onoffline | 
4  | 
≤79  | 
29  | 
No  | 
?  | 
8  | 
40  | 
40  | 
29  | 
?  | 
8  | 
4.0  | 
The WorkerGlobalScope interface it belongs to.
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    https://developer.mozilla.org/en-US/docs/Web/API/WorkerGlobalScope/onoffline