Modify values in an object recursively

applyToKeys.js

function applyToKeys(obj, modify) {
 let newObj = {}
 for (let [key, value] of Object.entries(obj)) {
  if (typeof value === 'object') {
   newObj[key]  = applyToKeys(obj[key], modify)
  } else {
   newObj[key] = modify(value)
  }
 }
 return newObj
}

// Example

let test = {
  x: 1,
  y: 2,
  z: {
    a: 1,
    b: 2,
  }
}

let example = applyToKeys(test, function(value) {
  return value + 1
})

// Expected result
// {
//  x: 2,
//  y: 3,
//  z: {
//   a: 2,
//   b: 3,
//  }
// }