javascript TextArea dynamically displays remaining characters

<div class="form">
<div class="con">
<ul>
<li>Limitation of remaining words</li>
<li><textarea cols="40" rows="8" ></textarea></li>
<li>Remaining characters:<span >/span></li>
</ul>
</div>
</div>

<script language="javascript">
var otext = ("text1");
var otextleft = ("textleft");
var re = /[^\x00-\xff]/g;
var maxLength = 40;
= function(){
if()
= textleft;
else
= textleft;
}
function textleft()
{
var str = ;
str = (re,"xx");// Chinese characters are processed as 2 characters. If not, the main line will be dropped
= maxLength - ;
}
</script>