Searching for an item in an array within MongoDB: Tips and techniques

Question

Searching for an item in an array within MongoDB: Tips and techniques

I am attempting to locate the object containing a specific element within an array:

Here is my query:

router.get('/', function(req, res) {
    var userSubscribed = req.user.email;
    db.posts.find({ "SubscriberList": { $elemMatch: userSubscribed}}, function(err, object){
        if (err) console.log(err);
        else console.log(object);
        res.render('index', { title: 'Home', user: req.user});
    })
});

The error message displayed is as follows:

{ [MongoError: Can't canonicalize query: BadValue $elemMatch needs an Object] name: 'MongoError'}

An example of an object in the database:

{ 
    "_id" : ObjectId("5490afa8416841105626cc41"), 
    "post" : { 
        "title" : "Ralph", 
        "category" : "Node", 
        "date" : "2014-12-11", 
        "description" : "Node coming soon!" 
    }, 
    "owner" : "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="e1838e9492808c9380cf93808d9189a1868c80888dcf828e8c">[email protected]</a>", 
    "status" : "active", 
    "category" : "Node", 
    "SubscriberList" : ["<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="f0919c91829993b0989f849d91999cde939f9d">[email protected]</a>" ]
}

javascript json mongodb

Answer 1

Answer №1

When dealing with an array of strings like the SubscriberList, there's no need to use $elemMatch unless you're trying to match multiple properties within a single array element.

To find posts where a user is subscribed, you can simply query:

router.get('/', function(req, res) {
    var userSubscribed = req.user.email;
    db.posts.find({ "SubscriberList": userSubscribed }, function(err, object){
        if (err) console.log(err);
        else console.log(object);
        res.render('index', { title: 'Home', user: req.user});
    })
});

Answer 2

When dealing with an array of strings like the SubscriberList, there's no need to use $elemMatch unless you're trying to match multiple properties within a single array element.

To find posts where a user is subscribed, you can simply query:

router.get('/', function(req, res) {
    var userSubscribed = req.user.email;
    db.posts.find({ "SubscriberList": userSubscribed }, function(err, object){
        if (err) console.log(err);
        else console.log(object);
        res.render('index', { title: 'Home', user: req.user});
    })
});

Answer 3

Answer №2

Give this code a shot:

router.get('/', function(req, res) {
var userSubscribed = req.user.email;
db.posts.find({owner:userSubscribed}, function(err, data){
    if (err) console.log(err);
    else console.log(data);
    res.render('index', { title: 'Home', user: req.user});
})
});

Answer 4

Give this code a shot:

router.get('/', function(req, res) {
var userSubscribed = req.user.email;
db.posts.find({owner:userSubscribed}, function(err, data){
    if (err) console.log(err);
    else console.log(data);
    res.render('index', { title: 'Home', user: req.user});
})
});

Searching for an item in an array within MongoDB: Tips and techniques

Answer №1

Answer №2

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