JS实现文本框宽高实时调整功能

<html>
<head>
<title>改变文字区域的高宽</title>
<script language="javascript">
<!--
 function addrows(){
  rows = form1.txt.rows;
  rows++;
  form1.txt.rows = rows;
 }
 function addcols(){
  cols = form1.txt.cols;
  cols++;
  form1.txt.cols = cols;
 }
//-->
</script>
</head>
<body>
<form name="form1">
 <textarea name="txt"></textarea>
 <input type="button" value="增加高" onClick="addrows()">
 <input type="button" value="增加宽" onClick="addcols()">
</form>
</body>
</html>