JavaScriptValidPalindrome.md

JavaScript Valid Palindrome

Challenge

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.

Given a string s, return true if it is a palindrome, or false otherwise.

1^st Example

Input: s = 'A man, a plan, a canal: Panama'
Output: true
Explanation: 'amanaplanacanalpanama' is a palindrome.

2^nd Example

Input: s = 'race a car'
Output: false
Explanation: 'raceacar' is not a palindrome.

3^rd Example

Input: s = ' '
Output: true
Explanation: s is an empty string '' after
             removing non-alphanumeric characters.
             Since an empty string reads the same
             forward and backward, it is a palindrome.

Constraints

• 1 <= s.length <= 2 * 10⁵
• s consists only of printable ASCII characters.

Solution

const isPalindrome = (s) => {
    let sanitizedString = s.replace(/\W|_/g,''),
        reversedString  = sanitizedString.split('')
                                         .reverse()
                                         .join('');

    return sanitizedString.toLowerCase() == reversedString
                                            .toLowerCase();
};

Explanation

I've built a function expression, using ES6 syntax, that is defined by an anonymous function that accepts s as a string of words.

Within the anonymous function, I establish a variable for the input string called sanitizedString which takes the string s and applies the string prototype method replace to remove the non-alphanumeric characters with the help of regex.

I also set a variable called reversedString to reverse the sanitizedString. I apply the string prototype method split to create an array for every character of the sanitizedString, then I use the array prototype reverse method to reverse the order of the string characters within the array, and then I use the array prototype join method to turn the reversed character array back into a string that can be referred to as reversedString.

The sanitizedString and reversedString variables have the string prototype toLowerCase method applied to make sure all the characters are in lower case. The two variables are then compared to each other for basic equality and a Boolean value is returned.

⏭️ Next (Reverse Vowels of a String)

⏮️ Previous (Reverse Words in a String III)

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