js textarea自动下拉(带计数)图

<div> </div> <textarea cols="30" rows="5" id="a"> </textarea> <script language="javascript"> document.onkeydown=function() { str=a.value.replace(/[^x00-xff]/g,"aa") b.innerHTML=str.length+1 if(str.length+1>150) { a.style.overflow="visible" } } </script>
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]