Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.
You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
ECMAScript 6 (or ECMAScript 2015) 标准中对参数引入了一些新的特性：剩余参数(rest parameters)，函数参数默认值，解构等。