How to return Node.js callback
You can't return from a callback - see this canonical about the fundamental problem. Since you're working with Mongoose you can return a promise for it though:
var getApps = function(searchParam){ var appsInCategory = Model.find({ categories: searchParam}); return appsInCategory.exec().then(function (apps) { return apps; // can drop the `then` here });}Which would let you do:
getApps().then(function(result){ // handle result here});