node.js - how to add pagination to node/express api -

in mean app, have controller, serves following api:

app.get('/mongodata', function(req, res){         console.log('request successful');         console.log('_parsedurl.query:  ' + req._parsedurl.query);          var url_parts = requesturl.parse(req.url, true);         var query = url_parts.query;          var dataversion = req.query.dataversion;          mongoclient.connect(url, function (err, db) {             if (err) {                 console.log('unable connect mongodb server. error:', err);             } else {                 console.log('connection established to', url);                  var collection = db.collection(query.collectionname);                  collection.find({dataversion: query.dataversion}).toarray(function(err, docs) {                     //console.log(docs);                     res.json(docs);                     assert.equal(null, err);                     db.close();                 });              }         });     }); 

what proper technique / syntax add pagination capability api?