Javascriptはユーザー登録の検証を実現する.

function isRight(){

    //         
    var username=document.getElementById("username").value;
    if(username==""||username==null){
        alert("       ！！");
        return false;
    }

    //    
    var password=document.getElementById("password").value;
    if(password==""||password==null){
        alert("      ！！");
        return false;
    }
    var password2=document.getElementById("password2").value;
    if(password2==""||password2==null){
        alert("       ");
        return false;
    }

    //            
    if(password!=password2){
        alert("          ！！");
        return false;
    }

    //          
    var email=document.getElementById("email").value;
    if(!/^[a-z0-9]+([._\\-]*[a-z0-9])*@([a-z0-9]+[-a-z0-9]*[a-z0-9]+.){1,63}[a-z0-9]+$/.test(email)){
        alert("         ");
        return false;
    }
}

<form action="#" method="get"  onsubmit="return isRight()">
                <table border="0px" cellpadding="5px" cellspacing="0xp">
                    <th colspan="2">
                          
                    th>
                    <tr>
                        <td>
                            <span>
                                   :
                            span>
                        td>
                        <td>
                            <input id="username" type="text" name="username"/>
                        td>
                    tr>
                    <tr>
                        <td>
                            <span >
                                  :
                            span>
                        td>
                        <td>
                            <input id="password" type="password" name="password"/>
                        td>
                    tr>
                    <tr>
                        <td>
                            <span>
                                       ：
                            span>
                        td>
                        <td>
                            <input id="password2" type="password" name="password2"/>
                        td>
                    tr>
                    <tr>
                        <td>
                            <span>
                                    :
                            span>
                        td>
                        <td>
                            <input id="email" type="text" name="emial"/>
                        td>
                    tr>
                    <tr>
                        <td>
                            <span>
                                    :
                            span>
                        td>
                        <td>
                            <input id="epassword" type="password" name="epassword"/>
                        td>
                    tr>
                    <tr>
                        <td colspan="2" style="text-align: center;">
                            <input type="submit" value="  "/>
                        td>

                    tr>
                table>

            form>