Lvzl Blog来源 力扣（LeetCode）
给你单链表的头节点 head ，请你反转链表，并返回反转后的链表
输入：head = [1,2,3,4,5] 输出：[5,4,3,2,1]
输入：head = [1,2] 输出：[2,1]
js
var reverseList = function (head) {
let prev = null; //上一个
let current = head; // 当前
while (current) {
const next = current.next; //
current.next = prev;
prev = current;
current = next;
}
return prev
};