What are the advantages and disadvantages of using NativeScript with Angular+TypeScript and NativeSCript with JavaScript. I want to know which would be better approach in terms of difficulty and Performance.
Typescript is compiled to Javascript, so there are no performance impact between the two.
If you know C# or Java, you already know most of the Typescript. Typescript adds... types to variables and objects, which makes your code much more stable by providing your IDE with the necessary informations to warn you about eventual bugs.