How to write Mongoose Queries with optional express query-params?

Question

I am building a REST API on top of Express 4. For a path lets say GET /api/users I want to query my users collection accordingly to optional queryParams.

So a call to the API could look like this host:port/api/users?city=Berlin

In this case name is omitted and doesn't influence the query, whereas city has to match.

I managed to do this with the following hack. Is there a better way than that?

Users.statics.customFilter = function(qP){
    return this.find({
        $and: [
            {$or: [{undefined: {$eq: qP.city}}, {'city': qP.city}]},
            {$or: [{undefined: {$eq: qP.name}}, {'name': qP.name}]}
        ]
    });

mongoose.model('User', Users);

I'm calling this static function from the mongoose schema like this...

const User = mongoose.model('User');
app.get('/api/users', (req, res) => {
        User.customFilter(req.query)
        .exec((err, results) => {
            if (err) return next(err);
            res.json(results);
        });
    });

Solution

It seems to me that in essence, User.find(req.query) should do what you want:

/api/users?city=Berlin           → User.find({ city : 'Berlin' })
/api/users?name=John             → User.find({ name : 'John' })
/api/users?name=John&city=Berlin → User.find({ city : 'Berlin', name : 'John' })

Of course, you have to decide what should happen if no parameters are passed (in the example above, it would become a query that would match all users, which may not be what you want).

Also, you should probably filter req.query so it only contains fields that are defined in your schema.

Comments

[fight_club]

Refer stackoverflow.com/questions/57001644/…

[Ludwig Goohsen]

ah cool, that's a start. But what if I don't test for equality, nor strings. So {$or: [{undefined: {$eq: qP.ageLower}}, {'age': {$gte: parseInt(qP.ageLower)}}]} wouldn't work like this, right? Also I'm having nestled fields I want to query. So the queryParameter city should actually test against address.city. Any ideas?

[robertklep]

If you need more than simple equality checking you're going to have to process the incoming data anyway, or allow a more elaborate query format to be used (mongo-rql, monquery, mongo-querystring).