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, value) {
  return keys.split('.')
    .reverse()
    .reduce((acc, current) => ({
      [current]: acc
    }), value);
}

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