Object / Array Traversal - Recursive Solution

object-traversal.js

// Recursive inline function
function get(obj, path = '') {
  return (function _get(obj, parts) {
    return (obj === undefined || parts.length === 0) ? obj : _get(obj[parts.shift()], parts);
  })(obj, path.split('.'));
}

// Pure recursion
function get(obj, path = '') {
  const parts = Array.isArray(path) ? path : path.split('.');
  return (obj === undefined || parts.length === 0) ? obj : get(obj[parts.shift()], parts);
}

// "Tests"
console.log(get({a: {b: { c: 5 } } }, 'a')); // { b: {c: { 5 }} }
console.log(get({a: {b: { c: 5 } } }, 'a.b')); // { c: 5 }
console.log(get({a: {b: { c: 5 } } }, 'a.b.c')); // 5
console.log(get({a: {b: { c: 5 } } }, 'a.b.bad')); // undefined

console.log(get({a: {b: { c: [1, 2, { d: 'Yes!' }] } } }, 'a.b.c.0')); // 1
console.log(get({a: {b: { c: [1, 2, { d: 'Yes!' }] } } }, 'a.b.c.1')); // 2
console.log(get({a: {b: { c: [1, 2, { d: 'Yes!' }] } } }, 'a.b.c.2')); // { d: 'Yes!' }
console.log(get({a: {b: { c: [1, 2, { d: 'Yes!' }] } } }, 'a.b.c.2.d')); // 'Yes!'

console.log(get(undefined, undefined)); // undefined
console.log(get(undefined, 'a.b.c')); // undefined