js去空格键 js过滤特殊字符

<script>
function trim(inputstring) {
if (typeof inputstring != "string") { return inputstring; }
 var retvalue = inputstring;
 var ch = retvalue.substring(0, 1);
 while (ch == " ") {
     //检查字符串开始部分的空格
     retvalue = retvalue.substring(1, retvalue.length);
     ch = retvalue.substring(0, 1);
 }
 ch = retvalue.substring(retvalue.length-1, retvalue.length);
 while (ch == " ") {
    //检查字符串结束部分的空格
    retvalue = retvalue.substring(0, retvalue.length-1);
    ch = retvalue.substring(retvalue.length-1, retvalue.length);
 }
 while (retvalue.indexof("  ") != -1) {
          //将文字中间多个相连的空格变为一个空格
    retvalue = retvalue.substring(0, retvalue.indexof("  ")) + retvalue.substring(retvalue.indexof("  ")+1, retvalue.length);
 }
 return retvalue;
}
//-->
</script>

<script>
function checkifenglish( string )
{
    var letters = "(!@#$%^&*;':)";
     var i;
     var c;
      if(string.charat( 0 )=='-')
 return false;
      if( string.charat( string.length - 1 ) == '-' )
          return false;
 for( i = 0; i < string.length; i ++ )
     {
          c = string.charat( i );
   if (letters.indexof( c ) > 0)
    return false;       
     }
     return true;
}
</script>

<script language="javascript">
//更多过滤特殊字符，自行补充到new array("char","varcahr","#");
function checkforms()
{
   var iu, iuu, regarray=new array("char","varcahr","#","admin");
   iuu=regarray.length;
   var obj=document.getelementbyid("username");
   if(obj.value=="")
   {
     alert("用户名不能为空");
      obj.focus();
      return false;
   }
   for(iu=1;iu<=iuu;iu++)
   {  
      if(regarray[iu] !="")
       {
          if (obj.value.indexof(regarray[iu])!=-1)
           {
alert("注册名不可以包含：" + regarray[iu]);
document.gforms.username.focus();
return false;
          }
        }
   }
   return true;
}
</script>

<form method="post" onsubmit="return checkforms();">
请输入用户名:<input type="text" name="username">
<input type="submit" name="submit" value="提交">
</form>