ES6 flatten object function

flattenObject.js

// {
//   foo: {
//     bar: "0",
//     baz: {
//       hello: "world"
//     }
//   }
// }
// ...becomes...
// {
//   foo/bar: "0",
//   foo/baz/hello: "world"
// }
function flattenObject (obj) {
  let result = {}

  for (let key of Object.keys(obj)) {
    let val = obj[key]

    // recur
    if (typeof val == 'object' && val !== null && val.constructor == Object) {
      let flattened = flattenObject(val)
      for (let flatKey of Object.keys(flattened)) {
        result[key + '/' + flatKey] = flattened[flatKey]
      }
    }
    // base
    else {
      result[key] = val
    }
  }

  return result
}