银行卡号4位隔开

[javascript]代码库

<script type="text/javascript">  
        window.onload =function() {  
            document.getElementById("bank_account_id").onkeyup =function() {  
                this.value =this.value.replace(/\s/g,'').replace(/(\d{4})(?=\d)/g,"$1 ");
            };  
        };  
    </script>