What is the proper syntax for Premium and Non Premium Account Names?

Question

I don't think this is correct for standard names and also neglects premium names.

https://developers.eos.io/eosio-cpp/docs/naming-conventions

I came up with this, please let me know if it is incorrect:

Non Premium Account Names (gu3tambwg3ge):

Can only contain the characters abcdefghijklmnopqrstuvwxyz12345 a-z (lowercase), 1-5
Must be 12 characters

Excluded:

Must start with a letter - https://bloks.io/account/1b5gii3jjnz2
Must not end in a dot - cannot have a dot at all unless premium
and . (period) - cannot have a dot

Premium Account Names (xyz.xyz)

Can only contain the characters .abcdefghijklmnopqrstuvwxyz12345 a-z (lowercase), 1-5 and . (period)
12 characters max
1 characters min (Todd says premium names can start with a dot)
Must not end in a dot

This is a valid premium name: ....a..a.a ~ Todd

https://bloks.io/account/.a.p.p.l.e

https://bloks.io/account/e

Answer 1

You can use:

const validateEos = (address) => {
    // can make lowercase:
    if(address.match(/[A-Z]/)) address = address.toLowerCase();

    if(!/^[a-z1-5.]+$/.test(address)) {
        console.log('Contains an invalid character')
        return false;
    }
    if(address.match(/[.]/i)) {
        if(address.length !== 12) {
            console.log('Non premium name must be 12 characters')
            return false;
        }
    }
    if(address.slice(-1) === '.') {
        console.log('Premium name cannot end with "."')
        return false;
    }
    return true;
};

export default validateEos;