[GitHub] [cordova] breautek commented on issue #303: Control of the WebView from an independent javascript instance.

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breautek commented on issue #303:
URL: https://github.com/apache/cordova/issues/303#issuecomment-1368484057

   I'm not certain how feasible this is due to the architecture of Cordova but Android has an experimental [JavaScriptEngine](https://developer.android.com/jetpack/androidx/releases/javascriptengine) package, which allows you to build a javascript environment without a webview.
   
   In theory this could be used for background processing as it can be done in a service/WorkManager task.
   
   There are a few limitations of this however, one is that the [JavaScriptSandbox](https://developer.android.com/reference/kotlin/androidx/javascriptengine/JavaScriptSandbox) may be only supported on API 26 or newer devices, and only if the installed android webview has support for it.
   
   > Note: Applications must check JavaScriptSandbox availability by calling [JavaScriptSandbox.isSupported()](https://developer.android.com/reference/kotlin/androidx/javascriptengine/JavaScriptSandbox#isSupported()) API. Make sure that the application verifies that the sandbox is supported on the device before calling any other JavaScriptSandbox methods. The sandbox is supported on API 26 and above if the WebView implementation supports it.
   
   JavaScriptEngine is not production ready so it's not something Cordova can use right now, and even if it was, we would need to bump our min SDK to at least API 26. So it's not something I can see being implemented in the foreseeable future, but it would be an interesting experiment, which potentially be a cordova plugin.
   
   iOS also has a similar system called [JavaScriptCore](https://developer.apple.com/documentation/javascriptcore?language=objc) which is available as of iOS 16.0, so similar story to Android... in order to use this feature, it will need to bump our min version to iOS 16 which is too restrictive at this time. But likely implementable in the form of a plugin as an experiment.
   
   > I'm not certain how feasible this is due to the architecture of Cordova
   
   Coming back to this, the main concern I have is Cordova makes a lot of assumptions and I don't think plugins will necessary have a guaranteed opportunity to control the webview instance just after the webview instance is created, short of implementing your own webview plugin. And if the JS is running in a background/service thread, it may not have safe access to the webview instance either.


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