Configuration variables in Svelte / Sapper

rollup.config.js

import conf from 'config'

const appConfig = Object.keys(conf).reduce((acc, n) => {
	acc[`process.env.${n}`] = JSON.stringify(conf[n])
	return acc
}, {})

export default {
	client: {
		...,
		plugins: [
			...
			replace({
				'process.browser': true,
				'process.env.NODE_ENV': JSON.stringify(mode),
				...appConfig
			}),
			...
		]
	}
}