This function traverse the hole object and checking whether the object value of each layer has a nested object or not

isNestedObject.js

function isObject(obj){
  return (typeof obj === 'object') ? true : false;
}

function traverse (json, callback) {
  JSON.parse(json, function (key, value) {
    if (key !== '') {
      callback.call(this, key, isObject(value))
    }
    return value
  })
}

traverse('{"a":{"b":{"c":{"d":1}},"e":{"f":2}}}', function (key, value) {
  console.log(key+ " : " +value)
})