难度: 简单
/**
* @param {string} s
* @return {boolean}
*/
var isPalindrome = function (s) {
s = s.replace(/[^0-9a-zA-Z]/g, '').toLowerCase();
let left = 0;
let right = s.length - 1;
while (left < right) {
if (s[left] !== s[right]) return false;
left++;
right--;
}
return true;
};