Question

我在result中查询了我的查询结果，但我无法将其传递给浏览器，它显示为空。如何将result返回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();
    });
});

res.send(result);

}）;

Answer 1

你有2个解决方案：

将res.send(result);放在console.log(result)

承诺包装您的MongoClient.connect，如下所示：

let promise = new Promise((resolve,reject)=>{
  MongoClient.connect(url,function(err,db){
    db.collection('projects').aggregate([{$match:{school_state:"DC"}}, {$group:{_id: "$primary_focus_subject",total_amount:{$sum: "$total_donations"}}}],function(err,result){
      if(err) reject(err)
      resolve(result);
    });
  });    
})

从node.js中的嵌套回调中返回变量

1 个答案: