Setting a deep JSON property with one call, a answer to a question on StackOverflow that was deleted before I could post it https://stackoverflow.com/questions/47064851/read-or-init-js-variable-to-avoid-cannot-read-property-of-undefined#47064851

deepSet.js

function deepSet(keys, defaultValue) {
  var keyNames = keys.split('.')
  var out = defaultValue
  var temp
  var size = keyNames.length
  var i

  for (i = size - 1; i >= 0; i--) {
    temp = out
    out = {}
    out[keyNames[i]] = temp
  }

  return out
}

//You can use it like this:
console.log(JSON.stringify(deepSet('foo.name.social.twitter.followers', 100)))
//OUTPUTS:
//{"foo":{"name":{"social":{"twitter":{"followers":100}}}}}