網上找了很多,這個比較實在
<html>
<textarea rows="7" cols="49" id="box" οnclick=tellPoint()>
fasdfsdafsdafsafsadsdfsdfasfsafdsadfsadfsaf
</textarea>
<script language="javascript">
function tellPoint()
{
var rng = event.srcElement.createTextRange();
rng.moveToPoint(event.x,event.y);
rng.moveStart("character",-event.srcElement.value.length);
pnum.value = rng.text.length;
}
</script> <p></p>
光標位置：<input type="text" value="0" id="pnum" size="8">
</html>