JS uses regular rules to control user input and formatting of bank card numbers

This article introduces to you through example code the method of using js to control the user's input of bank card number and formatting using regular expressions. The code is simple and easy to understand, very good, and has reference value. Friends who need it can refer to it

//js regular implementation of the control and formatting of bank card number input by users

<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">

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