如何使用Javascript正确验证此表单

我有一个类似的javascript表单：

<form id="loginForm" name="loginForm" action="/create_session/" method="post">{% csrf_token %}
    <table border="0" cellpadding="0" cellspacing="0" id="id-form">
        <tr>
            <th valign="top"></th>
            <td>
                <div class="error_main">
                    <p style="color: #009900; font-size: 13px; font-weight: bold;"><span style="color:red;">{{ server_error }}</span> {{ connec_ok }}{{ successful }}</p>
                </div>
            </td>
            <td></td>
        </tr>
        <tr>
            <th valign="top">Session Name :</th>
            <td>
                <input id="session_name" {{ disabled }} value="{{ session_name }}" name="session_name" class="inp-form" type="text" onchange="validateSessionName()" />
            </td>
            <td id="session_error"></td>
            <td></td>
        </tr>
        <tr>
            <th valign="top">Source Server Path :</th>
            <td>
                <input id="server_path" {{ disabled }} value="{{ server_path }}" name="server_path" onchange="validatePath()" class="inp-form" type="text" />
            </td>
            <td id="path_error"><span style="color:black"><em>Eg: 10.1.1.43:/home/sachet/test_data</em></span>
            </td>
            <td></td>
        </tr>
        <tr>
            <th valign="top">Source username :</th>
            <td>
                <input id="source_username" {{ disabled }} name="source_username" class="inp-form" type="text" onchange="validateUsername()" />
            </td>
            <td id="username_error"></td>
            <td></td>
        </tr>
        <tr>
            <th valign="top">Source Password :</th>
            <td>
                <input id="source_password" {{ disabled }} name="source_password" class="inp-form" type="password" onchange="validatePassword()" />
            </td>
            <td id="password_error"></td>
            <td></td>
        </tr>
        <tr>
            <th valign="top"></th>
            <td>
                <input name="make_default" {{ disabled }} {{ checked }} type="checkbox" id="make_default" />
                <label style="font-size: 13px;" for="make_default">Make the session default</span>
            </td>
        </tr>
        <tr>
            <th>&nbsp;</th>
            <td valign="top">
                <input type="submit" name="create_session" value="Submit" id="submit" class="form-submit" />
                <input type="reset" value="Reset" class="form-reset" />
                <td></td>
        </tr>
    </table>
    <!-- end id-form -->
</form>

我想对给定的表单进行两种验证。除了Make default复选框外，每个输入框都不应该为空。我希望每个字段都满足这个正则表达式：

filter = /^[A-Za-z0-9]+$/;

当用户点击Submit按钮而不填写任何值时，我想在每个字段的右侧显示所需的字段。此外，如果用户在填写表单时不满足输入字段，我想显示无效数据，因此我添加了onchange。我已经完成了onchange部分，现在如果用户提交空表单，我想在每个字段上显示所需的字段

$(document).ready(function() {
    $("#submit").click(function(){
        var session_name    =   $("#session_name").attr("value");
        var server_path     =   $("#server_path").attr("value");
        var source_username =   $("#source_username").attr("value");
        var source_password =   $("#source_password").attr("value");
        if(session_name==''){
            document.getElementById('session_error').innerHTML="Field Required!";
            document.getElementById('submit').disabled=false;
        }
        else if(server_path==''){
            document.getElementById('path_error').innerHTML="Field Required!";
            document.getElementById('submit').disabled=false;
        }
        else if(source_username==''){
            document.getElementById('username_error').innerHTML="Field Required!";
            document.getElementById('submit').disabled=false;
        }
        else if(source_password==''){
            document.getElementById('password_error').innerHTML="Field Required!";
            document.getElementById('submit').disabled=false;
        }
        else{
            return true;
        }
    });
});