https://leetcode.com/problems/masking-personal-information

function maskPII(s: string): string {
    if (s.includes('@')) {
        const [name, domain] = s.toLowerCase().split('@');
        const newName = name.charAt(0) + '*****' + name.charAt(name.length-1);
        return `${newName}@${domain}`;
    } else {
        const numbers = s.replace(/[^0-9]/g, '');
        const last = numbers.substring(numbers.length-4);
        const cd = numbers.length - 10;
        switch(cd) {
            case 0:
                return `***-***-${last}`;
            case 1:
                return `+*-***-***-${last}`;
            case 2:
                return `+**-***-***-${last}`;
            case 3:
                return `+***-***-***-${last}`;
        }
        throw numbers;
    }
};