ref: https://github.com/parcel-bundler/parcel/issues/969

index.js

import { add } from './math.rs'

console.log(add(1, 2))

math.rs

#[no_mangle]
pub fn add(a: i32, b: i32) -> i32 {
    a + b
}

package.json

{
  "name": "parcel-wasm-for-node",
  "version": "0.0.0",
  "main": "index.js",
  "license": "MIT",
  "scripts": {
    "build": "parcel build -t node -o dist/bundle.js index.js",
    "start": "node dist/bundle.js",
    "prestart": "npm run build"
  },
  "devDependencies": {
    "parcel-bundler": "^1.6.2"
  }
}