直接上实例
***buttom 提交****
<SCRIPT language="javascript">
function LoginOnsubmit()
{
if (document.Login.CardNum.value.length==0)
{
alert("请输入你的员工卡号码!");
document.Login.CardNum.focus();
return false;
}
if (document.Login.password.value.length==0)
{
alert("请输入密码!");
document.Login.password.focus();
return false;
}

document.getElementById("login").submit();

}
</SCRIPT>
<form action="?action=login" method="post" name="Login" id="login">
<div class="form-group">
<input type="button" value="登陆" class="btn btn-success" onclick="LoginOnsubmit();">
</div>
</form>
***submit提交，是一种特殊的提交**

<SCRIPT language="javascript">
function LoginOnsubmit()
{
if (document.Login.CardNum.value.length==0)
{
alert("请输入你的员工卡号码!");
document.Login.CardNum.focus();
return false;
}
if (document.Login.password.value.length==0)
{
alert("请输入密码!");
document.Login.password.focus();
return false;
}

//**document.getElementById("login").submit(); 这条可以不要，会自动提交

}
</SCRIPT>

<form onSubmit="return LoginOnsubmit()" action="?action=login" method="post" name="Login" >
<div class="form-group">
<input type="submit" value="登陆" class="btn btn-success" >
</div>
</form>