The easiest way to check if a string is a palindrome in TypeScript

is-palindrome.ts

const isPalindrome = (phrase: string): boolean => {
    const original = phrase.toLowerCase().replace(/[^A-Za-z0-9]/g, '');
    const reversed = original.split('').reverse().join('');

    return original === reversed
}

console.log(
    isPalindrome("A man, a plan, a canal – Panama!")
)

The regular expression:

/[^A-Za-z0-9]/g

means find non-alphanumeric characters globally. This part: [^] means "find not in this set" and A-Za-z0-9 means "alphanumeric characters".