var checkRegisterForm = function () {
    var username = document.getElementById('username');
    var password = document.getElementById('password');
    var password2 = document.getElementById('password-2');
    var error = document.getElementById('test-error');
    var reg = /^[0-9a-zA-Z]{3,10}$/;
    var reg2 = /^.{6,20}$/;
    if (!reg.test(username.value)) {
        error.innerText = 'username error';
        return false;
    } else if (!reg2.test(password.value)) {
        error.innerText = 'password error';
        return false;
    } else if (password.value !== password2.value) {
        error.innerText = 'password2 error';
        return false;
    } else {
        return true;
    }
}