websql 修改数据时InvalidStateError: DOM Exception 11

//文件删除与修改  
    function changeDir (id,s) {  
        var db=window.openDatabase("localNote","1.0","用于离线存储笔记文件",1024*1024*50);  
        var btnArr=['取消','确定'];  
        if (db) {  
            if (s==1) {//删除  
                mui.confirm('您将删除该文件夹及其含有的文件？','删除文件夹',btnArr,function (e) {  
                    if (e.index==1) {  
                        db.transaction(function(jz){  
                           jz.executeSql("delete from dir where id="+id);  
                           mui.toast('删除成功！');  
                        })  
                    } else{  
                        mui.toast('您取消了删除操作！');  
                    }  
                },'div');  
            }  
            if (s==2) {//修改  
                var dirname = null;  
                db.transaction(function(jz){  
                   jz.executeSql("select dirname from dir where id="+id,[],function (jz,rs) {  
                     dirname=rs.rows.item(0)['dirname'];  
                     mui.prompt(' ',dirname,'修改文件名',btnArr,function (e) {  
                        if (e.index==1&&e.value.length>0) {  
//                          jz.executeSql("select * from dir",[],function (jz,rs) {  
//                              //避免文件夹重名  
//                              var b=true;  
//                              for(var i=0,len=rs.rows.length;i<len;i++){  
//                                  if (rs.rows.item(i)['dirname']==e.value) {  
//                                      b=false;  
//                                  }  
//                              }  
                                console.log(id);  
                                var sql="update dir set dirname='"+e.value+"' where id="+id;  
                                console.log(sql);  
                                jz.executeSql(sql);// 这里报错，求大神看看啊！  
                                mui.toast('修改成功！');  
//                          });  
                        }else{  
                            mui.toast('您取消了修改操作！');  
                        }  
                    },'div');  
                   });  
                })  
            }  
        }  
        localDB();  
    }

数据删除与插入都没有问题啊！！！就是更新数据时报错[ERROR] : InvalidStateError: DOM Exception 11: An attempt was made to use an object that is not, or is no longer, usable.