JS实现文本框随内容长度动态调整宽度

<!Doctype HTML PUBLIC "-//W3c//DTD Html 1.0 Transitional//EN">
<html>
<head>
<title>文本框随文本的宽度而增长</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>
<input type="text" size="3" id="text" onkeydown="changeInputlength(this);"/>
<span id="countFont"></span>
</body>