To be clear, you can compile to WASM with emscripten. However, if you want to call JavaScript code, e.g. to interact with the DOM from WASM in browser, then the bindings that are declared in the standard library will not work.

Instead, you will need to write your own bindings. Here's an example repository of mine using emscripten with Nim: https://github.com/miguelmartin75/nim-wasm-experiments and here are bindings to emscripten's C API for websockets: https://github.com/miguelmartin75/nim-wasm-experiments/blob/...

With emscripten, you can create bindings to JavaScript using EM_JS macros, which you can emit in Nim. Here is an example of how to do so: https://github.com/treeform/windy/blob/bc98d4642c700f0277551...