firebaseRefHelper.js

const cloudDb = new Firebase(FIREBASE_URL);

// ref helper
function getRef(...args) {
  return args.reduce((result, key) => result.child(key), cloudDb);
}

// example usage
const box = {some: 'new property'};
const projectId = 1;
const boxId = 2;

getRef('data/projects', projectId, 'boxes', boxId).update(box);