2. Add Two Numbers

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var addTwoNumbers = function (node1, node2) {
	let addedLL = { val: 0, next: null },
		carryOver = 0,
		dummyHead = addedLL

	while (node1 || node2) {
		let currSum, currNode
		const node1Val = node1 ? node1.val : 0
		const node2Val = node2 ? node2.val : 0
		currSum = node1Val + node2Val + carryOver

		if (currSum < 10) {
			currNode = { val: currSum, next: null }
			carryOver = 0
		} else if (currSum > 9) {
			currNode = { val: currSum % 10, next: null }

			carryOver = Math.floor(currSum / 10)
		}

		addedLL.next = currNode
		addedLL = addedLL.next

		if (node1) {
			node1 = node1.next
		}
		if (node2) {
			node2 = node2.next
		}
	}

	if (carryOver > 0) {
		addedLL.next = { val: carryOver, next: null }
	}

	return dummyHead.next
}

node1 = {
	val: 2,
	next: { val: 4, next: { val: 3, next: { val: 9, next: null } } },
}
node1 = { val: 2, next: { val: 4, next: { val: 3, next: null } } }
node2 = { val: 5, next: { val: 6, next: { val: 4, next: null } } }
// node1 = { val: 9, next: null }
// node2 = { val: 9, next: null }

//Test cases
console.log(JSON.stringify(addTwoNumbers(node1, node2)))