Mix + custom API for separate builds

webpack.mix.js

const mix = require("laravel-mix")

mix.site = (id, callback) => {
    if (!process.env.SITE || process.env.SITE === id) {
        return callback()
    }
};

mix.site('admin', () => {
    mix.js("resources/js/admin/app.js", "public/js/admin.js")
    mix.sass("resources/sass/admin/app.scss", "public/css/admin.css")
})

mix.site('app', () => {
    mix.js("resources/js/app.js", "public/js")
    mix.sass("resources/sass/app.scss", "public/css/app.css")
})

// run using:
// SITE=admin yarn run dev
// SITE=app yarn run dev