The following function will return true if str is a palindrome; otherwise, it returns false.

palindrome.js

// isPalindrome("level");   // Outputs true 
// isPalindrome("levels");   // Outputs false
// isPalindrome("A car, a man, a maraca");   // Outputs true


function isPalindrome(str) {
    // We will replace any non-word character with empty place. 
    // Lowercase all string
    str = str.replace(/\W/g, '').toLowerCase();

    // First use split in order to convert string to array.
    // So, every single character is different array instance.
    // Reverse the array. Use join to convert array into string.
    console.log(str == str.split('').reverse().join(''));
}