JS去除字符串两边空格

<HTML>
<HEAD>
<META http-equiv="Content-Type" content="text/html; charset=gb2312">
<TITLE>JS去除左右空格</TITLE>
<SCRIPT language="javascript">
function LTrim(str){ //去掉字符串 的头空格

var i;

for(i=0;i<str.length;i++){
  if(str.charAt(i)!=" "&&str.charAt(i)!=" ") {
	   break;
   } 
}

str = str.substring(i,str.length);

return str;

}

function RTrim(str){

var i;

for(i=str.length-1;i>=0;i--){

if(str.charAt(i)!=" "&&str.charAt(i)!=" ") break;

}

str = str.substring(0,i+1);

return str;

}

function Trim(str){

document.getElementById('unRemove').innerText=document.getElementById('str').value;
document.getElementById('remove').innerText=LTrim(RTrim(str));

}
//var s=Trim("   asd     ");
//alert(s);
</SCRIPT>
</HEAD>

<BODY>
请出入字符串：<INPUT id="str" type="text" ><BR>
<INPUT type="button" value="去除空格" onClick="Trim(document.getElementById('str').value)"><BR>
未去空格：
<SPAN style="background-color:#FF0000" id="unRemove"></SPAN><BR>
去除空格：
<SPAN style="background-color:#FF00FF" id="remove"></SPAN><BR>
</BODY>
</HTML>