206-Reverse Linked List.js

/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function(head) {
    if (!head) { return head; }
    let prev = null, next = null, curr = head;
    while(curr) {
        next = curr.next;
        curr.next = prev;
        prev = curr;
        curr = next;
    }
    head = prev;

    return head;
};