Can Nativescript build apps for web as well?
As Ionicframework and similar uses Cordova to build Android and iOS the same code there can be served by an HTTP server to the mobile or desktop browsers.
Will that be possible with the apps built with Nativescript, using same code base for web version of the app?
Nowadays Angular integration is on the way, and using Angular for the mvc kind of things (like data bindings, events etc.) and using Native for the device apis, platform apis and native gui would help in an unequaled way.
Angular parts can be used in the browser as well when built for it. What to do with the xml written for the gui templates in Nativescript, they could be converted to proper html for web built of the app, as Nativescript itself already uses a unified gui api for different platforms, that could be possible. And lastly, native calls made in NativeScript would be ignored in the web build.
It would be great to build for Android, iOS, and Web with the same exact code base.
tl;dr: No
Longer: The big difference between the Cordova/Phonegap based technologies (such as Ionic and Supersonic) and the Dynamic Runtime based technologies (such as NativeScript, React Native and Titanium) is that the first uses a HTML approach where the application is run by WebKit/Blink in a WebView. Looking on the Dynamic Runtime technologies there's no HTML Engine running your app, but rather native views and widgets. The framework (in this case NativeScript) is "just" a bridge between Javascript and the native language of the device.
However, depending of how you architecture your code, you can create Javascript which will be usable in both a NativeScript environment as well as in a browser environment.
Edit: The above means that you could reuse some of your code. There'll still be NativeScript specific code.
Edit2: There's an ongoing project to enable usage of Angular 2 in NativeScript. Please see current status in the issue: https://github.com/NativeScript/NativeScript/issues/103 Also note that the Telerik NativeScript core developer Valentin Stoychev is saying
So: Yes on code reuse - no on exact same codebase.