JavaScript 验证注册信息

  

<SCRIPT LANGUAGE="JavaScript" type="text/javascript">
<!--
function checks()
{
   if(checkspace(document.userinfo.Account.value)) {
 document.userinfo.Account.focus();
    alert("用户名不能为空，请重新输入！");
 return false;
  }
    if(checkspace(document.userinfo.Account.value) || document.userinfo.Account.value.length < 4) {
 document.userinfo.Account.focus();
    alert("用户名长度不能小于4，请重新输入！");
 return false;
  }
    if(checkspace(document.userinfo.userpassword.value) || document.userinfo.userpassword.value.length < 6) {
 document.userinfo.userpassword.focus();
    alert("密码长度不能小于6，请重新输入！");
 return false;
  }
    if(document.userinfo.userpassword.value != document.userinfo.userpassword1.value) {
 document.userinfo.userpassword.focus();
 document.userinfo.userpassword.value = '';
 document.userinfo.userpassword1.value = '';
    alert("两次输入的密码不同，请重新输入！");
 return false;
  } 
       if(checkspace(document.userinfo.zhuzhaitel.value)) {
 document.userinfo.zhuzhaitel.focus();
    alert("请输入您的住宅电话以便联系！");
 return false;
  }

 if(document.userinfo.useremail.value.length!=0)
  {
    if (document.userinfo.useremail.value.charAt(0)=="." ||        
         document.userinfo.useremail.value.charAt(0)=="@"||       
         document.userinfo.useremail.value.indexOf('@', 0) == -1 || 
         document.userinfo.useremail.value.indexOf('.', 0) == -1 || 
         document.userinfo.useremail.value.lastIndexOf("@")==document.userinfo.useremail.value.length-1 || 
         document.userinfo.useremail.value.lastIndexOf(".")==document.userinfo.useremail.value.length-1)
     {
      alert("Email地址格式不正确！");
      document.userinfo.useremail.focus();
      return false;
      }
  }
  else{
   alert("Email不能为空！");
   document.userinfo.useremail.focus();
   return false;
  }
    
}
//-->
</script>