updateObjectValuesRecursively.js

const typeOf = require('just-typeof')

/**
 * Update object values recursively
 * @param   {Object} obj
 * @param   {Function} handler
 * @returns {Object} - new object
 */
const updateObjectValuesRecursively = (obj, handler) => {
  const newObj = {}
  Object.keys(obj).forEach(key => {
    if (typeOf(obj[key]) === 'object') {
      newObj[key] = updateObjectValuesRecursively(obj[key], handler)
    } else {
      newObj[key] = handler(obj[key])
    }
  })
  return newObj
}

const obj = {
  a: 1,
  b: 'foo',
  c: {
    d: { e: 5 }
  }
}

const newObj = updateObjectValuesRecursively(obj, val => {
  if (typeof val === 'number') {
    return val * 10
  }
  return val
})

newObj