Can you get the loop ?.js

/*
Description:
You are given a node that is the beginning of a linked list. This list always contains a tail and a loop.

Your objective is to determine the length of the loop.

For example in the following picture the tail's size is 3 and the loop size is 11.

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// Use the `getNext' method or 'next' property to get the following node.

node.getNext()
node.next
Note: do NOT mutate the nodes!

Thanks to shadchnev, I broke all of the methods from the Hash class.

Don't miss dmitry's article in the discussion after you pass the Kata !!
*/
function loop_size(node){
  var turtle = node;
  var rabbit = node;
  
  // Find a point in the loop.  Any point will do!
  // Since the rabbit moves faster than the turtle
  // and the kata guarantees a loop, the rabbit will
  // eventually catch up with the turtle.
  do {
    turtle = turtle.getNext();
    rabbit = rabbit.getNext().getNext();
  }
  while (turtle != rabbit);
  
  // The turtle and rabbit are now on the same node,
  // but we know that node is in a loop.  So now we
  // keep the turtle motionless and move the rabbit
  // until it finds the turtle again, counting the
  // nodes the rabbit visits in the mean time.
  var count = 0;
  do {
    ++count;
    rabbit = rabbit.getNext();
  }
  while (turtle != rabbit);

  // voila
  return count;
}