Why would return in recursion return undefined?

Question

JavaScript

Why would return in the first example return undefined - https://jsfiddle.net/slavik_210/Lwp0bgr1/1/ ?
And if the result is saved to an external variable, then it works - https://jsfiddle.net/slavik_210/7x95ydjh/

Answer 1

The result of the recursion must also be returned:

if(list[i].children) {
  return getChildLists(list[i].children, name);
}

Answer 2

You look at the console.
There "(index):58 Uncaught ReferenceError: lists is not defined"