按find（）过滤-Javascript

我正在使用我的第一个NodeJS服务器，我正在努力。到现在为止，我有一个很好的工作，因为它是

工作

exports.getPosts = (req, res, next) => {
  const pageSize = +req.query.pagesize;
  const currentPage = req.query.page;
  const postMode = req.query.mode;
  postQuery = POST.find();
  let fetchedposts;

  if (pageSize && currentPage) {
    postQuery.skip(pageSize * (currentPage - 1))
      .limit(pageSize);
  }
  postQuery.find()
    .then(documents => {
      fetchedposts = documents;
      return post.count();
    }).then(count => {
      res.status(200).json({
        message: 'posts fetched successfully',
        posts: fetchedposts,
        maxposts: count
      });
    })
    .catch(error => {
      res.status(500).json({
        message: "Fetching posts failed"
      });
    });
};

exports.getposts = (req, res, next) => {
  const pageSize = +req.query.pagesize;
  const currentPage = req.query.page;
  const postMode = req.query.mode;
  postQuery = POST.find();
  let fetchedposts;

  if (pageSize && currentPage) {
    postQuery.skip(pageSize * (currentPage - 1))
      .limit(pageSize);
  }
  postQuery.find(**(post) => post.private === true**)
    .then(documents => {
      fetchedposts = documents;
      return post.count();
    }).then(count => {
      res.status(200).json({
        message: 'posts fetched successfully',
        posts: fetchedposts,
        maxposts: count
      });
    })
    .catch(error => {
      res.status(500).json({
        message: "Fetching posts failed"
      });
    });
};

但是现在我尝试向查询添加一个新参数mode。我试图实现的是通过向方法

find（）

添加额外属性来过滤列表。我尝试添加它们，如下代码所示：

不工作

exports.getPosts = (req, res, next) => {
  const pageSize = +req.query.pagesize;
  const currentPage = req.query.page;
  const postMode = req.query.mode;
  postQuery = POST.find();
  let fetchedposts;

  if (pageSize && currentPage) {
    postQuery.skip(pageSize * (currentPage - 1))
      .limit(pageSize);
  }
  postQuery.find()
    .then(documents => {
      fetchedposts = documents;
      return post.count();
    }).then(count => {
      res.status(200).json({
        message: 'posts fetched successfully',
        posts: fetchedposts,
        maxposts: count
      });
    })
    .catch(error => {
      res.status(500).json({
        message: "Fetching posts failed"
      });
    });
};

exports.getposts = (req, res, next) => {
  const pageSize = +req.query.pagesize;
  const currentPage = req.query.page;
  const postMode = req.query.mode;
  postQuery = POST.find();
  let fetchedposts;

  if (pageSize && currentPage) {
    postQuery.skip(pageSize * (currentPage - 1))
      .limit(pageSize);
  }
  postQuery.find(**(post) => post.private === true**)
    .then(documents => {
      fetchedposts = documents;
      return post.count();
    }).then(count => {
      res.status(200).json({
        message: 'posts fetched successfully',
        posts: fetchedposts,
        maxposts: count
      });
    })
    .catch(error => {
      res.status(500).json({
        message: "Fetching posts failed"
      });
    });
};

但是我的服务器崩溃了

错误

postQuery.find（（post）=>post.private==true）类型错误：无法读取null的属性“private”

---

我应该怎么做呢？

这个错误意味着

post

在某个点上是空的。您可以通过在检查私有值之前检查它是否为null来修复它：

---

（post）=>post&&post.private===true

什么是

post

，你不应该在分页之前进行过滤（获取所有

private

帖子）（跳过

和
限制
调用）？这是我尝试的第一件事，但同样失败了不，说真的，
post
是什么？