kentcdodds/cross-env

The **cross‑env** project lets you set environment variables in a single, platform‑agnostic way for scripts—most commonly npm scripts—so you can write `cross-env NODE_ENV=production …` once and have it work correctly on both Unix‑like systems and Windows. It’s aimed at developers who need reliable, cross‑platform environment‑variable handling without worrying about shell‑specific syntax or Windows quirks.