js屏蔽非法字符

<script>
//计算字符长度
function checkStrLen(string){
var str,Num = 0;
for(var i=0;i<string.length;i++){
  str = string.substring(i,i+1);
  if(str<="~"){  //判断是否双字节
      Num+=1;
  }else{
      Num+=3;
   }
 }
  return Num;
}

 

function check_data(){
var userformat=/^(\w|[\u4E00-\u9FA5])+$/
var emailformat=/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/
var nostr="51cto|51ct0|root|妈的|傻逼|王八|admin|管理|bbs|blog|group";
var pattern = new RegExp(nostr,"gi");

 //username
if(document.getElementById('username').value==""){
        alert("用户名不能为空。"); 
     document.getElementById('username').focus();
  document.getElementById('checkname').value = "0";
  return false;
    } else if(checkStrLen(document.getElementById('username').value)>15 || checkStrLen(document.getElementById('username').value)<4){
        alert("用户名请填写4-15个字符长度的中文/字母/数字，同时请勿使用特殊字符。"); 
     document.getElementById('username').focus();
  document.getElementById('checkname').value = "0";
  return false;
    } else if(!userformat.test(document.getElementById('username').value)){
    alert("用户名不能使用特殊字符。"); 
    document.getElementById('username').focus(); 
    document.getElementById('checkname').value = "0";
    return false;
 } else if(pattern.test(document.getElementById('username').value)){
    alert("用户名包含敏感字符或被系统屏蔽。"); 
    document.getElementById('username').focus(); 
    return false;
 } else if(document.getElementById('usernameexist').value==1){
    alert("此用户名已经被注册,请更换。"); 
    document.getElementById('username').focus(); 
    return false;
 } else {
  document.getElementById('checkname').value = "1";
 }
}
</script>

<form name="reg" action="" method="post" id="reg" onSubmit="return check_data()" autocomplete="off" >
 <input type="hidden" name="reback" value="http://www.51cto.com">
 <input type="hidden" name="fromuid" value="">
 <input type="hidden" name="reg_logfrom" value="http://www.51cto.com">
 <input type="hidden" name="checkname" id="checkname" value="0">
 <input name="step" type="hidden" value="1">
  <table width="620" border="0" align="center" cellpadding="0" cellspacing="0">

    <tr>
      <td height="18" colspan="3">&nbsp;</td>
      </tr>
    <tr>
      <td width="180" align="right" valign="bottom" class="font1">用户名：&nbsp;<span  style=" color:#FF0000">*</span>&nbsp;</td>
      <td width="2" rowspan="9" class="font2"></td>
      <td width="440" class="font2"> <input name="username" id="username" type="text teat1_1"  class="teat1" size="15"    onChange="usercheck('check')" onBlur="usercheck('check')" value=""  > </td>
    </tr>
    <tr>
      <td align="right" valign="bottom" class="font1">&nbsp;</td>
      <td height="30" valign="top" class="font2"><span id="check">4-15个字符长度的中文/字母/数字，请勿使用特殊字符</span></td>
    </tr>
    
    </table>
   <table width="620" border="0" align="center" cellpadding="0" cellspacing="0">
    <tr>
      <td colspan="2">&nbsp;</td>
    </tr>
    <tr>
      <td height="1" colspan="2" bgcolor="#EBEBEB"></td>
    </tr>
    <tr>
      <td height="22" colspan="2">&nbsp;</td>
    </tr>
    <tr>
      <td colspan="2" align="center"><input type="submit" value="提交">&nbsp; <input type="button" value="重置"  onclick="javascript:document.all.reg.reset();"/></td>
    </tr>
    <tr>
      <td height="22" colspan="2">&nbsp;</td>
    </tr>
  </table>
</form