If I'm using a third-party Javascript SDK inside a NativeScript application, in what cases would it break?
For instance, if the SDK does DOM manipulation, I'm assuming that NativeScript will be unable to handle that.
What about cases like where the SDK is just a wrapper over a REST API. So the SDK probably makes an XMLHTTP request internally. Would this be handled by NativeScript? XMLHTTP is a Web API so I'm not sure it would work correctly on Android/iOS.
Any other cases I'm missing?
(Specifically, I was wondering if the QuickBlox Javascript SDK would work directly in any such application I make)
Note that although both NativeScript and node.js have running JS VMs, they are implemented differently. NativeScript for example does not implement node.js' built-in modules specification (fs, stream, buffer, net, etc.). That is also the reason why you won't be able to use most of the node.js modules 'just like that'.
To use an npm module that relies on built-in node.js modules, you could try replacing the imports and functions yourself, or https://github.com/EddyVerbruggen/nativescript-nodeify#nativescript-nodeify
Bear in mind in NativeScript you can't use npm modules that manipulate the DOM either.
So in the case of QuickBox, you will want to use the mobile platform SDKs, and if you wish to make a plugin - wrap the two mobile platform sdks under a common JavaScript API.