<script language="javascript" type="text/javascript">
function formatBankNo (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;
}
</script>

<input type="text" value="" size="25" onkeyup="formatBankNo(this)" onkeydown="formatBankNo(this)" name="account" id="account">