Grab a Random Node

Given a linked list, can you write a method to get a random node within it? Let's assume you're given a random node generator. The linked list will have at least 2 nodes, and may look something like this:

1 -> 2 -> 3 -> 4

The odds of getting any number between 1 and 4 inclusive should be the exactly the same.

You have access to this definition of a Linked List node:

function Node(val) {
  this.val = val;
  this.next = null;
}

Constraints

• Length of the linked list <= 10000
• The nodes will always contain integer values between -1000000000 and 1000000000
• Expected time complexity : O(n)
• Expected space complexity : O(n)

```js
function fetchRandomNode(headNode) {
  // grab random node
  return headNode;
};

// function Node(val) {
//   this.val = val;
//   this.next = null;
// }
```