step307

function isValidSfId(str) {
    // https://stackoverflow.com/a/29299786/1333724
    if (typeof str !== 'string' || str.length !== 18) {
        return false;
    }

    let upperCaseToBit = (char) => char.match(/[A-Z]/) ? '1' : '0';
    let binaryToSymbol = (digit) => digit <= 25 ? String.fromCharCode(digit + 65) : String.fromCharCode(digit - 26 + 48);

    let parts = [