napi-rs/examples/napi/src/nullable.rs

use napi::bindgen_prelude::*;

#[napi]
fn map_option(val: Option<u32>) -> Option<u32> {
  val.map(|v| v + 1)
}

#[napi]
fn return_null() -> Null {
  Null
}

#[napi]
fn return_undefined() -> Undefined {}