在这里很难说出您要完成的工作，但这是一个开始 观点.我所做的主要更改是删除了两行

It's hard to tell what you are trying to accomplish here but here is a starting point. The main change I made was removing the two lines

// if true redirect
res.render('new-sensor-settings', { username: req.session.username, id: 'home', brand: brand })

因为那些是在回调之前执行的 db.collection.findOne，因此当 内部res.render被调用.我只是猜测这些行是 无关紧要的，也许是该函数先前迭代的遗留物.如果 它们不是偶然的，请提供有关该功能的更多信息 应该做.

because those were being executed before the callback of db.collection.findOne, and thus prevented a response from being sent when the inner res.render was called. I am just guessing that these lines are extraneous, perhaps a leftover from a previous iteration of the function. If they are not accidental, please provide more information about what the function should do.

我进行的其他较小更改:

Other minor changes I made:

缩进2个空格.

我在if(!req.query.sid)语句周围添加了花括号. (对 有没有大括号的单行if语句，但是更少 可维护的，所以我个人的喜好是始终添加它们.)

I added curly brackets around the if(!req.query.sid) statement. (it's fine to have one-line if statements without the curly brackets, but it's less maintainable, so my personal preference is to always add them.)

我在发送响应的语句之前添加了return.自从 res.redirect和res.render语句都放在它们的末尾 各自的if块，它们中的两个不再有任何执行的机会. 因此，这里的return并不是完全必要的-只是我个人的 使用它们的偏好，这明确表明现在响应已经 发送后，此路由中不应再执行任何代码.

I added return in front of the statements that send a response. Since the res.redirect and res.render statements are all placed at the end of their respective if blocks, there is no longer any chance of two of them executing. So the returns here aren't strictly really necessary - it's just my personal preference to use them, making it explicit that now that the response has been sent, no further code should be executed in this route.

我将if(!result)移到了附加到先前if(result)

I moved if(!result) into an else block attached to the previous if(result)

exports.sensorsettings = function(req, res){
  if (!req.session.username) {
    // if false render
    return res.render('login', { logo: 'img/owl.png', id: 'home', brand: brand })
  } else {
    if(!req.query.sid){ (return res.redirect('/dashboard')); }
    // get sid information from database
    db.collection('sensors').findOne({sid:req.query.sid}, function(err, result) {
      console.log('this is result:' + result);
      if (result) {
        console.log('this is result:' + result.name);
        // Problem here too:
        result= JSON.stringify(result);
        // result is now a string, trying to access properties will be undefined
        return res.render('new-sensor-settings', { username: req.session.username, name:result.name,
          ipaddress: result.ipaddress, desc: result.desc, snmpcom: result.snmpcom, snmpver: result.snmpver,
          snmpport: result.snmpport, snmpifindex: result.snmpifindex, ncusername: result.ncusername,
          ncport: result.ncport})
      } else {
        return res.redirect('/errors?err=db');
      };
    });
  }
};