js 验证特殊字符
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
 <HEAD>
  <TITLE> New Document </TITLE>
  <META NAME="Generator" CONTENT="EditPlus">
  <META NAME="Author" CONTENT="">
  <META NAME="Keywords" CONTENT="">
  <META NAME="Description" CONTENT="">
  <script language="javascript">    
function isCheckNumber(){ 
   var numbercard=document.forms[0].num.value;  
 var numberpattern =/^[A-Za-z0-9_]{1,8}$/;
      if(!numberpattern.test(numbercard)){
	   alert("
请输入有效的 只能是1-8位数字,字母或数字字母的组合");
	   document.forms[0].num.focus();
         return false;
       }
return true;
}    
  </script>
 </HEAD>
 <BODY>
  <form>  
  number:<input type="text" name="num" id="num" onblur="
isCheckNumber()" value=""/>  
  </form>
 </BODY>
</HTML>