N-API register module (the new way)

binding.gyp

{
  "targets": [
    {
      "target_name": "hello",
      "sources": [ "hello.cc" ]
    }
  ]
}

gistfile1.txt

'use strict'

const addon = require('bindings')('hello');

console.log(addon.hello()); // 'world'

hello.cc

#include <assert.h>
#include <node_api.h>

napi_value Method(napi_env env, napi_callback_info info) {
  napi_status status;
  napi_value world;
  status = napi_create_string_utf8(env, "world", 5, &world);
  assert(status == napi_ok);
  return world;
}

#define DECLARE_NAPI_METHOD(name, func)                                        \
  { name, 0, func, 0, 0, 0, napi_default, 0 }

extern "C" {

  napi_value napi_register_module_v1(napi_env env, napi_value exports) {
    napi_status status;
    napi_property_descriptor desc = DECLARE_NAPI_METHOD("hello", Method);
    status = napi_define_properties(env, exports, 1, &desc);
    assert(status == napi_ok);
    return exports;
  }

}

//NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)

In WIndows you need to add __declspec(dllexport) like reported below:

#include <assert.h>
#include <node_api.h>

napi_value Method(napi_env env, napi_callback_info info) {
  napi_status status;
  napi_value world;
  status = napi_create_string_utf8(env, "world", 5, &world);
  assert(status == napi_ok);
  return world;
}

#define DECLARE_NAPI_METHOD(name, func)                                        \
  { name, 0, func, 0, 0, 0, napi_default, 0 }

extern "C" {

  napi_value __declspec(dllexport) napi_register_module_v1(napi_env env, napi_value exports) {
    napi_status status;
    napi_property_descriptor desc = DECLARE_NAPI_METHOD("hello", Method);
    status = napi_define_properties(env, exports, 1, &desc);
    assert(status == napi_ok);
    return exports;
  }

}

//NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)

for msys2/mingw you have to use

g++ -shared -fPIC  hello.cc -lnode -o hello.node

and #include <node/node_api.h> instead of just node_api.h
then test:
echo "console.log(require('./hello.node').hello())" | node -

@Kreijstal thank you!