If you want to make a JS version, WebAssembly might be a great way to package the code up. WASM is fully supported in nodejs now, and its available in all modern browsers[1]. You'd need to write bindings for the C++ API methods, but once you do that you could throw the result up on npm and it should work in both node and web projects, with no compilation step.
To your library's users the end result will be indistinguishable from a native JS library.
Edit: I just had a play to see how feasible this would be. Even a stripped, optimized build of tink compiles into a 2.5MB binary. This would be fine from nodejs, but its way too big for a web library. It would need to be heavily cut down to be useful in a browser. It might be easier to simply wrap the modern browser crypto API.
[1] https://caniuse.com/#feat=wasm