Node.js函数中的异步混乱

Question

I always have multiple operations in one route or endpoint. Take an example below, when a user deletes an item, I want the related file be deleted in s3 too besides deleting related collection from the database.

So is the code below ok? Does it matter if I put the first function (delete file from s3) inside the DeleteItem function?

router.post('/item/delete', function(req, res) {

  if(req.body.dlt_item){

        var tempArray = [];
        tempArray.push({"Key":req.body.dlt_item});

        s3Bucket.deleteObjects({
              Bucket: 'myS3',
              Delete: {
                  Objects: req.body.dlt_item
              }
          }, function(err, data) {
              if (err) 
                return console.log(err);
        });
      }

  Item.DeleteItem(req.body.item_id, function(err,result){
    if(err){console.log(err)}
    res.send({result:1});
  })
});

Answer 1

You should organise your code like this. This will ensure that s3 deletion will start only when mongodb deletion has finished. In your code both things happen simultaneously. this may cause issue in some cases. If one fails and other succeeds then there will be trouble.
Suppose s3 files get deleted successfully and mongo deletion fails. Then you will have many references to non existing resources.

 router.post('/item/delete', function(req, res) {

if(req.body.dlt_item){
    var tempArray = [];
    tempArray.push({"Key":req.body.dlt_item});
 Item.DeleteItem(req.body.item_id, function(err,result){
   if(err)
   {
     console.log(err)
     res.send(err);
   }
  else
   {
          //deletion from mongodb is succesful now delete from s3
           s3Bucket.deleteObjects({
           Bucket: 'myS3',
           Delete: {
              Objects: req.body.dlt_item
           }
         },function(err, data) {
           if (err) 
           {
             // deletion from s3 failed you should handle this case
             res.send({result:1});
             return console.log(err);
           }
           else
             {
                // successful deletion from both s3 and mongo. 
               // If you do not want to wait for this then send the response before this function.
               res.send({result:1});
             }
        });
   }      
  })
});