Dynamic queries in MongoDB and Node.js

express, mongodb, mongodb-query, node.js

Solution

Build up your query object programmatically:

var query = {'film_id': {$in : genre}};
if (param) {
    query._id = {$lt: tokenId};
} else {
    query._id = {$gt: tokenId};
}
collection.find(query).sort({'_id': -1}).limit(25).toArray(function(error, films);

Update

Now that Node.js 4+ supports computed property names, you can create `query` in one step as:

var query = {
    film_id: {$in: genre},
    _id: {[param ? '$lt' : '$gt']: tokenId}
};

Problem

I am working on a nodejs/express app with Mongodb on the backend. In one of my API calls, depending on the presence of a particular querystring parameter or the other I want to issue a query to Mongodb with either a $gt or a $lt. In some cases we want to ask for everything less than the `tokenId` using $lt, but in other cases we want everything greater than the `tokenId` using $gt. How do we do that without duplicating the queries? Here's an example query: ``` collection.find({'film_id': {$in : genre}, '_id': {$lt: tokenId}}).sort({'_id': -1}).limit(25).toArray(function(error, films) ``` Is there a way to dynamically create the query without actually doing 2 different queries?

Original source