nodejs 中间件执行在 return 之后继续

Question

我有以下中间件：

const mongoose = require('mongoose');

module.exports = function(req, res, next) {
  const keys = Object.keys(req.params);
  keys.forEach(elem => {
    if (
      (elem.includes('id') || elem.includes('Id')) &&
      !mongoose.Types.ObjectId.isValid(req.params[elem])
    )
      return res
        .status(400)
        .json({ msg: `id: ${req.params[elem]} is invalid` });
  });
  next();
};

它在获取请求中被调用：

// @route   GET api/movies/:id
// @desc    Get a movie with specified id from db
// @access  Public
router.get('/:id', checkId, async (req, res) => {
const movie = await Movie.findById(req.params.id);
res.json(movie);
});

当我在邮递员中使用无效 ID（例如：1234）发出请求时，我收到的正确响应是 400，其中包含 msg: 'id 1234 is invalid' 但执行仍然传递给请求回调代码，错误是当我尝试访问具有无效 ID 的数据库时抛出。

所以问题是为什么中间件仍然允许执行 next()，即使它已经返回 400？

Answer 1

您需要通过调用 next("some-error") 告诉路由器出现问题。例如，您可以这样做：

module.exports = function(req, res, next) {
  const keys = Object.keys(req.params);
  keys.forEach(elem => {
    if (
      (elem.includes('id') || elem.includes('Id')) &&
      !mongoose.Types.ObjectId.isValid(req.params[elem])
    ) {
      res
        .status(400)
        .json({ msg: `id: ${req.params[elem]} is invalid` });
      return next("invalidinput");
    }
  });
  next();
};

或者如果您愿意，您可以通过在路由器外部设置结果来更通用，如下所示：

在你的中间件中：

module.exports = function(req, res, next) {
  const keys = Object.keys(req.params);
  keys.forEach(elem => {
    if (
      (elem.includes('id') || elem.includes('Id')) &&
      !mongoose.Types.ObjectId.isValid(req.params[elem])
    ) {
      // === Report the error and let the router handle it
      return next({
        type: "invalidinput",
        msg: `id: ${req.params[elem]} is invalid`
      );  
    }
  });
  next();
};

然后在路由器的底部：

// handle any errors
router.use(err, req, res, next) => {
  if (err) {
    if (err.type === "invalidinput") {
      return req.status(400).json({msg: err.msg});
    }
    else {
      return res.status(500).json({msg: "Internal error."});
    }
  }
  return next();
}

Answer 2

另一种可能的解决方案是将 forEach 转换为经典的 for 循环，从而使这个中间件运行同步

module.exports = function(req, res, next) {
  const keys = Object.keys(req.params);
  for (let i = 0; i < keys.length; i++) {
    if (
      (keys[i].includes('id') || keys[i].includes('Id')) &&
      !mongoose.Types.ObjectId.isValid(req.params[keys[i]])
    )
      return res
        .status(400)
        .json({ msg: `id: ${req.params[keys[i]]} is invalid` });
  }
  next();
};

nodejs 中间件执行在 return 之后继续

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