如果没有发现 .find() mongoose 就做点什么 [英] Do something if nothing found with .find() mongoose

问题描述

我正在 mongodb 中存储一些数据并使用 js/nodejs 和 mongoose 访问它.我可以使用 .find() 在数据库中找到一些东西就好了，这不是问题.问题是如果没有什么，我想做点别的.目前这就是我正在尝试的:

I'm storing some data in a mongodb and accessing it with js/nodejs and mongoose. I can use .find() to find something in the database just fine, that isn't an issue. What is a problem is if there isn't something, I'd like to do something else. Currently this is what I'm trying:

UserModel.find({ nick: act.params }, function (err, users) {
  if (err) { console.log(err) };
  users.forEach(function (user) {
    if (user.nick === null) {
      console.log('null');
    } else if (user.nick === undefined) {
      console.log('undefined');
    } else if (user.nick === '') {
      console.log('empty');
    } else {
      console.log(user.nick);
    }
  });
});

当我做一些act.params不在昵称索引中的事情时，这些都不会触发.发生这种情况时，我根本没有得到任何安慰，但我确实让 user.nick 在它实际存在时记录得很好.我只是试着像这样反向做:

None of those fire when I do something where act.params wouldn't be in the nick index. I don't get anything to console at all when this happens, but I do get user.nick to log just fine when it's actually there. I just tried to do it in reverse like this:

UserModel.find({ nick: act.params }, function (err, users) {
  if (err) { console.log('noooope') };
  users.forEach(function (user) {
    if (user.nick !== '') {
      console.log('null');
    } else {
      console.log('nope');
    }
  });
});

但这仍然没有记录nope.我在这里错过了什么?

but this still didn't log nope. What am I missing here?

如果它没有找到它，它只是跳过 find 调用中的所有内容，这很好，除非我需要在之后做一些事情，如果它不存在我不想做的事情.:/

If it doesn't find it, it just skips everything in the find call, which is fine, except I need to do things afterwards if it isn't there that I don't want to do if it is. :/

推荐答案

当没有匹配项时 find() 返回 []，而 findOne() 返回 null.所以要么使用:

When there are no matches find() returns [], while findOne() returns null. So either use:

Model.find( {...}, function (err, results) {
    if (err) { ... }
    if (!results.length) {
        // do stuff here
    }
}

或:

Model.findOne( {...}, function (err, result) {
    if (err) { ... }
    if (!result) {
        // do stuff here
    }
}

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