本段javascript代码，是操作网页中表单时，取得input或textarea当前光标的位置，知道光标位置之后，就可以在当前光标处，添加、删除某个字符,取得input中光标所在位置、在光标后面添加字符、删除光标前的字符
代码
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>无标题文档</title>
</head>
<body>
<script language="JavaScript">
function cc(a)
{
form1.username.focus();
var s=document.selection.createRange();
s.setEndPoint("StartToStart",form1.username.createTextRange());
var l=s.text.length;
alert("光标所在伴置："+l);
var str=form1.username.value.substring(0,l)+a+form1.username.value.substring(l,form1.username.value.length);
form1.username.value=str;
alert("在光标中间新增字符："+a);
}
</script>
<form name="form1" method="post" action="">
<p>
<input name="username" type="text" id="username" value="123456789" size="50">
</p>
<p>
<input type="button" name="Submit" value="测试" onclick='cc("zuoyefeng")'>
</p>
</form>
</body>
</html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>无标题文档</title>
</head>
<body>
<script language="JavaScript">
function cc(a)
{
form1.username.focus();
var s=document.selection.createRange();
s.setEndPoint("StartToStart",form1.username.createTextRange());
var l=s.text.length;
alert("光标所在伴置："+l);
var str=form1.username.value.substring(0,l)+a+form1.username.value.substring(l,form1.username.value.length);
form1.username.value=str;
alert("在光标中间新增字符："+a);
}
</script>
<form name="form1" method="post" action="">
<p>
<input name="username" type="text" id="username" value="123456789" size="50">
</p>
<p>
<input type="button" name="Submit" value="测试" onclick='cc("zuoyefeng")'>
</p>
</form>
</body>
</html>
