如何使用 mongoose 在 MongoDB 中搜索数组

Question

I am currently trying to find if an array of strings contains a certain string. So far, what I have is:

Following.find({ username: username }, { following: { $in: [profileUsername] } }).exec((err, result) => {
    if (err) {
        console.log(err);
        res.json(err);
    } else {
        res.json(result);
    }
});

However, it says that $in expects two arguments. Is there any better way to check whether the array contains the string? Thanks

Answer 1

$in doesn't receive 2 arguments, you just have a syntax error, the second object find receives is query options, not a query. You want to rewrite your query like so:

Following.find({ username: username, following: { $in: [profileUsername] } }).exec((err, result) => {
    if (err) {
        console.log(err);
        res.json(err);
    } else {
        res.json(result);
    }
});

Answer 2

You don't need to use the $in query filter as this is to match an item within a list of items, you can just do a normal equality

Following.find({ username: username, following: profileUsername } })

Checkout the mongo playground example: https://mongoplayground.net/p/cPF484_xqW5