get.js

const getAll = (userUID) => {
	return new Promise((resolve, reject) => {
		const ref = database
		.ref('user_data')
		.child(userUID)
		.child('customers')
		.on('value', snap => {
			(snap.val() ? resolve(snap.val()) : reject({'message': 'Empty Firebase node'}))
		})
	})
}