Flatten out a nested JSON object.

dottify.js

// Examples
//  To make this functions goal more clear, here are some example inputs with their expected outputs.
/*
const examples = [
  {
    input: { name: 'Ryan' },
    output: { name: 'Ryan' }
  },
  {
    input: { name: { first: 'Ryan', last: 'Haskell-Glatz' } },
    output: { 'name.first': 'Ryan', 'name.last': 'Haskell-Glatz' }
  },
  {
    input: { name: 'Ryan', age: 24 },
    output: { name: 'Ryan', age: 24 }
  },
  {
    input: {
      name: { first: 'Ryan', last: 'Haskell-Glatz' },
      birthday: { year: 1993, month: 'Nov' }
    },
    output: {
      'name.first': 'Ryan',
      'name.last': 'Haskell-Glatz',
      'birthday.year': 1993,
      'birthday.month': 'Nov'
    }
  }
]
*/

const isObject = (thing) =>
  thing && typeof thing === 'object'

const dottifyWithPrefix = (keyPrefix, obj) =>
  Object.keys(obj)
    .reduce((kvps, key) => {
      const newKvps = isObject(obj[key])
        ? dottifyWithPrefix(keyPrefix + key, obj[key])
        : [ { key: keyPrefix + key, value: obj[key] } ]
      return [ ...kvps, ...newKvps ]
    }, [])

const kvpsToObject = (obj, { key, value }) => {
  obj[key] = value
  return obj
}

const dottify = (obj) =>
  dottifyWithPrefix('', obj)
    .reduce(kvpsToObject, {})

module.exports = dottify