125. Valid Palindrome

/**
 * @param {string} s
 * @return {boolean}
 */
var isPalindrome = function(s) {
    s = s.replace(/[^a-z0-9]/gi,'').toLowerCase();
    let n = s.length;

    for(let i = 0; i <= n/2; i++){
        if(s[i] !== s[n-i-1]){
            return false;
        }
    }
    return true;
};