js插入字符到textarea的效果代码

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> 
<title>www.gxlcms.com js插入字符到textarea脚 本之家</title> 
<script language="javascript" type="text/javascript"> 
function grin(tag) { 
        var myField; 
        myField = document.getElementById('content'); 
        if (document.selection) { 
                myField.focus(); 
                sel = document.selection.createRange(); 
                sel.text = tag; 
                myField.focus(); 
        } 
        else if (myField.selectionStart || myField.selectionStart == '0') { 
                var startPos = myField.selectionStart; 
                var endPos = myField.selectionEnd; 
                var cursorPos = endPos; 
                myField.value = myField.value.substring(0, startPos) 
                                          + tag 
                                          + myField.value.substring(endPos, myField.value.length); 
                cursorPos += tag.length; 
                myField.focus(); 
                myField.selectionStart = cursorPos; 
                myField.selectionEnd = cursorPos; 
        } 
        else { 
                myField.value += tag; 
                myField.focus(); 
        } 
} 
</script> 
</head>

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]