does it have any api to communicate with js

[jjhesk]

I need a library to communicate messages with js for browser frontend.

[ftsf]

Nim<->JS is possible via emscripten, though it's not simple to use.

https://emscripten.org/docs/porting/connecting_cpp_and_javascript/Interacting-with-code.html (Nim acts as C++ here)