js给dropdownlist添加选项的小例子

  <input name="" type="text"  id="newDirtxt"/> <input class="btn" name="" type="button" value="创建新目录"  onclick="newDir()" /> 
 

?<BR><BR><BR>Js代码 <BR><BR><script type="text/javascript"> 
////创建新目录 
        function newDir() { 
            var txt = document.getElementById("newDirtxt"); 
            var dirname = txt.value; 
            if (dirname) { 
                alert("请填写目录名"); 
            } else { 
                $.ajax({ 
                    type: "Post", 
                    url: "/center/directorynew", 
                    async: false, 
                    data: { dirname: dirname }, 
                    success: function(msg) { 
                        if (msg.length < 40) { 
                            var DirectoryID = document.getElementById("DirectoryID"); 
                            var tOption = document.createElement("Option"); 
                            tOption.text = dirname; 
                            tOption.value = msg; 
                            DirectoryID.appendChild(tOption); 
                            txt.value = ""; 
                            alert("增加成功"); 
                        } else { 
                            alert("增加失败"); 
                        } 
                    } 
                }); 
            }//else 
        } 
    </script><BR><BR><BR>后台代码 <BR><BR>返回刚刚插入的目录的id字符串 <BR>