return variable from a nested callback in node.js
问题 I have the results of my query in result but I can not pass it to browser, it is showing empty. how can I return the result to res.send('result') ? myApp.get('/agg',function(req,res){ MongoClient.connect(url, function(err, db) { // Execute aggregate, notice the pipeline is expressed as an Array db.collection('projects').aggregate([{$match:{school_state:"DC"}}, {$group:{_id: "$primary_focus_subject",total_amount:{$sum: "$total_donations"}}}],function(err,result){ console.log(result); db.close(