sum list

Write a function, sumList, that takes in the head of a linked list containing numbers as an argument. The function should return the total sum of all values in the linked list.

test_00:

const a = new Node(2);
const b = new Node(8);
const c = new Node(3);
const d = new Node(-1);
const e = new Node(7);

a.next = b;
b.next = c;
c.next = d;
d.next = e;

// 2 -> 8 -> 3 -> -1 -> 7

sumList(a); // 19

test_01:

const x = new Node(38);
const y = new Node(4);

x.next = y;

// 38 -> 4

sumList(x); // 42

test_02:

const z = new Node(100);

// 100

sumList(z); // 100

test_03:

sumList(null); // 0