JavaScript实现按回车键登录的三种方法

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>Check Score</title>
<script language="JavaScript">
function keyLogin(){
 if (event.keyCode==13)  //回车键的键值为13
   document.getElementByIdx_x("input1").click(); //调用登录按钮的登录事件
}
</script>
</head>
<body onkeydown="keyLogin();">
<input id="input1" value="登录" type="button" onClick="alert('调用成功！')">
</body>
</html>

<script>
function KeyDown()
{
  if (event.keyCode == 13)
  {
    event.returnValue=false;
    event.cancel = true;
    Form1.btnsubmit.click();
  }
}
</script>

<form name="Form1" method="">
用户名:<INPUT TYPE=text SIZE=20 maxlength = 8 onkeydown=KeyDown()>
密码:<INPUT TYPE=password SIZE=20 maxlength = 8 onkeydown=KeyDown()>
<input type="submit" name="btnsubmit" value="提交" />
</form>

<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<link rel="stylesheet" href="css/text.css" type="text/css">
</head>
<body bgcolor="#FFFFFF" text="#000000" leftmargin="0" topmargin="0" marginwidth="0" marginheight="0" onkeydown="on_return();">
  <form name ="loginForm" method="post" action="fuck.html">        
   <table width="100%" border="0" cellspacing="0" cellpadding="0">
 <tr>
 <td width="69%" height="30"><span class="font_04">帐户名</span>
  <input type="text" name="userName" size="18.5">
 </td>
    </tr>
    <tr>
 <td width="69%" height="30"><span class="font_04">密　码</span>
  <input type="password" name="pwd" >
 </td>
    </tr>
    <tr>
 <td width="31%" height="30">
 <a id="sub" onClick='check()' >
 登陆</a></td>
    </tr>
   </table>
  </form>
</body>
</html>
<script language="javascript">
function check() {
    var formname=document.loginForm;
   if (formname.userName.value == "") {
    alert("请输入用户名！");
    formname.userName.focus();
    return false;
  }
  if (formname.pwd.value == "") {
    alert("请输入密码！");
    formname.pwd.focus();
    return false;
  }
  formname.submit();
}
  //回车时，默认是登陆
 function on_return(){
 if(window.event.keyCode == 13){
  if (document.all('sub')!=null){
   document.all('sub').click();
   }
 }
 }
</script>