Walking through a tree, combining reduce and recursion

n-tree-replace.js

const tree = {
  obj1: {
    obj2: {
      key1: 'key1'
    },
    obj3: {
      obj4: {
        key2: 'key2'
      }
    }
  },
  obj5: {
    key3: 'key3'
  }
}

const replacePattern = val => ({ value: val })

const replaceTree = obj =>
  Object
    .entries(obj)
    .reduce((acc, [key, val]) => {
      acc[key] = (val === Object(val))
        ? replaceTree(val)
        : replacePattern(val)
      return acc
    }, {})

const newTree = replaceTree(tree)

console.log(newTree)  // { obj1: { obj2: { key1: [Object] }, obj3: { obj4: [Object] } }, obj5: { key3: { value: 'key3' } } }

console.log(newTree.obj1.obj2.key1)        // { value: 'key1' }
console.log(newTree.obj1.obj3.obj4.key2)   // { value: 'key2' }
console.log(newTree.obj5.key3)             // { value: 'key3' }