Here is a quick solution to Reverse Linked List problem.
/**
* Definition for singly-linked list.
* function ListNode(val, next) {
* this.val = (val===undefined ? 0 : val)
* this.next = (next===undefined ? null : next)
* }
*/
/**
* @param {ListNode} head
* @return {ListNode}
*/
var reverseList = function(head) {
let curr = head;
let prev = null;
while (curr) {
let next = curr.next;
curr.next = prev;
prev = curr;
curr = next;
}
return prev;
};