var checkRegisterForm = function () {
    var userRe = /^[0-9a-zA-Z]{3,10}$/;
    var userName = document.getElementById('username').value;
    if(userRe.test(userName)){
        var password = document.getElementById('password').value;
        if(password.length < 6 || password.length > 20)
            return false;
        if(password !== document.getElementById('password-2').value)
            return false;
        return true;
    }
        return false;
}