jsp中回車提出フォーム

   function tijiao() {
        var loginForm = document.getElementById("loginForm");
        if (loginForm.login_name.value == "") {
            alert("      ");
            return;
        }
        if (loginForm.pwd.value == "") {
            alert("      ");
            return;
        }
        if (loginForm.validatacode.value == "") {
            alert("       ");
            return;
        }

        loginForm.action = "<%=path%>/memberlogin.action";
        loginForm.submit();
    }

  <form id="loginForm" method="post" onsubmit="javascript:tijiao()">

                <ul>
                    <li class="login_L_1"></li>
                    <li class="login_L_2">
                        <div align="center">${errMsg}</div>
                        <p>    ：
                            <select name="login_type">
                                <option value="loginname">   </option>
                             
                        <option value="email">    </option>
                            </select>
                        </p>
                        <p>   ：<input type="text" value="" name="login_name" size="27"/></p>

                        <p> 　 ：<input type="password" value="" name="pwd" size="27"/></p>

                        <p>   ：<input type="text" value="" name="validatacode" size="10"/>
                            <img src="<%=path %>/getImage.action" id="validataimage" border="0"/>
                        </p>


                        <p>
                            <input type="submit" name="Submit" value=" 　 "  onclick="javascript:tijiao();"
                                   class="blueButtonCss"/>　　
                            <input type="button" name="Submit3" value="    " onclick="javascript:chongzhi();"
                                   class="blueButtonCss"/>
                        </p>
                    </li>
                    <li class="login_L_3"></li>
                </ul>

            </form>