JavaScript实现文本框宽度随内容自适应

<!Doctype HTML PUBLIC "-//W3c//DTD Html 1.0 Transitional//EN"> 
<html> 
<head> 
<title>文本框宽度自动适应文本宽度</title> 
</head> 
<script type="text/javascript"> 
function changeInputlength(cursor) 
{ 
var getcount=document.getElementById("countFont"); 
var getText=document.getElementById("text"); 
getcount.innerHTML='<font>第'+(parseInt(getText.value.length)+1)+'个字符</font>'; 
cursor.size=getText.value.length+2; 
} 
</script> 
<body> 
请输入字符：<input type="text" size="3" id="text" onkeydown="changeInputlength(this);"/> 
<span id="countFont"></span> 
</body> 
</html>