in windows :
thats worked for me without any require in webpack.mix
... just add a new variable in env file with this prefix : MIX_
MIX_API_URL=http://laravel:8000
but need to restart php artisan serve and also restart npm run watch....
let api_url = process.env.MIX_API_URL;
console.log("my env variable:");
console.log(api_url);