JavaScript表单验证是'；t检查错误

我在php文件的头部有以下JavaScript代码：

<script language="JavaScript" type="text/javascript">
        function validateFirstName(field)
        {
            if (field == "")
            {
                return "Please enter a first name.'n";
            }
            else if (/[^a-zA-Z]/.test(field))
            {
                return "Invalid first name.'n";
            }
            return "";
        }
        function validateLastName(field)
        {
            if (field == "")
            {
                return "Please enter a last name.'n";
            }
            else if (/[^a-zA-Z]/.test(field))
            {
                return "Invalid last name.'n";
            }
            return "";
        }
        //more functions eliminated
        function validate(form)
        {
            fail = validateFirstName(form.firstname.value);
            fail += validateLastName(form.lastname.value);
            //and so forth
            if (fail == "")
            {
                return true;
            }
            else
            {
                alert(fail);
                return false;
            }
        }
    </script>

形式：

<form action="StudentSignUpPageAddingData.php" method="post" onsubmit="return validate(this)">
    <p id="p3">First Name: <input id="roundedcorners" type="text" name="firstname"><br></p>
    <p id="p3">Last Name: <input id="roundedcorners" type="text" name="lastname"><br></p>
//and so forth
    <input id="i1" type="submit" value="Done!">
</form>

不过，当我运行它时，程序会跳到StudentSignUpPageAddingData.php中的代码。我是php和JavaScript的新手，所以我想知道onsubmit调用是否有问题。我是否也应该考虑将JavaScript代码粘贴到一个单独的文件中，并简单地在PHP文件中引用它？