"join" for objects (Promise.props)

index.js

export default function using(hash, fn) {
	if (typeof fn !== 'function') {
		throw new Error('Missing expected function argument')
	}
	return Promise.all(Object.values(hash)).then((values) =>
		fn(
			Object.fromEntries(
				Object.keys(hash).map((key, idx) => [key, values[idx]])
			)
		)
	)
}