Get LinkedList length

function getLinkedListLength(A = [1,4,-1,3,2]) {
	let count = 0;
	let current = 0;

	while(current !== -1) {
    if (A.length < current)
      throw Error(`No link found for value: ${current}. Count: ${count}`); 
    
		current = A[current];
		count++;
	}

	return count;
}