js实现模拟银行卡账号输入显示效果

<script language="javascript" type="text/javascript">
function www_jb51_net (BankNo)
{
if (BankNo.value == "") return;
var account = new String (BankNo.value);
account = account.substring(0,22); /*帐号的总数, 包括空格在内 */
if (account.match (".[0-9]{4}-[0-9]{4}-[0-9]{4}-[0-9]{7}") == null)
{
/* 对照格式 */
if (account.match (".[0-9]{4}-[0-9]{4}-[0-9]{4}-[0-9]{7}|" + ".[0-9]{4}-[0-9]{4}-[0-9]{4}-[0-9]{7}|" +
".[0-9]{4}-[0-9]{4}-[0-9]{4}-[0-9]{7}|" + ".[0-9]{4}-[0-9]{4}-[0-9]{4}-[0-9]{7}") == null)
{
var accountNumeric = accountChar = "", i;
for (i=0;i<account.length;i++)
{
accountChar = account.substr (i,1);
if (!isNaN (accountChar) && (accountChar != " ")) accountNumeric = accountNumeric + accountChar;
}
account = "";
for (i=0;i<accountNumeric.length;i++)
{ /* 可将以下空格改为-,效果也不错 */
if (i == 4) account = account + "-"; /* 帐号第四位数后加空格 */
if (i == 8) account = account + "-"; /* 帐号第八位数后加空格 */
if (i == 12) account = account + "-";/* 帐号第十二位后数后加空格 */
account = account + accountNumeric.substr (i,1)
}
}
}
else
{
account = " " + account.substring (1,5) + " " + account.substring (6,10) + " " + account.substring (14,18) + "-" + account.substring(18,25);
}
if (account != BankNo.value) BankNo.value = account;
}
function checkBankNo (BankNo)
{
if (BankNo.value == "") return;
if (BankNo.value.match (".[0-9]{4}-[0-9]{4}-[0-9]{4}-[0-9]{7}") == null)
{
if (BankNo.value.match ("[0-9]{19}") != null)
www_jb51_net (BankNo)
}}
function checkEnterForFindListing(e){
var characterCode;
if(e && e.which){
e = e;
characterCode = e.which ;
}
else{
e = event;
characterCode = e.keyCode;
}
if(characterCode == 22){
document.forms[getNetuiTagName("findListingForm")].submit();
return false;
}
else{
return true ;
}}
</script>
只能输入数字，并且每输入4位数字会增加一个 - <br />
<input type="text" value="" size="25" onkeyup="www_jb51_net(this)" onkeydown="www_jb51_net(this)" name="account" id="account">