125. Valid Palindrome

Description:

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

For example,
"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.

Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.

For the purpose of this problem, we define empty string as valid palindrome.

My code:

/**
 * @param {string} s
 * @return {boolean}
 */
var isPalindrome = function(s) {
    let arrBefore = s.toUpperCase().match(/[a-zA-Z0-9]+/g);
    if(arrBefore == null) {
        return true;
    }
    let strBefore = arrBefore.join('');
    let strReverse = strBefore.split('').reverse().join('');
    if(strBefore == strReverse) {
        return true;
    } else {
        return false;
    }
};

Note: 字符串使用match()和toUpperCase()分别去除不需要的字符和忽略大小写，然后转换为数组取反，取反前后的字符串对比是否相等，如果相等即满足回文