遍历数组并执行MongoDB查询（NodeJS）

Question

I have an object name profile that contains a favorites array that looks like this...

{favorites: [
    { name: 'Love Song',
      id: 'Itja90E2tIE'},
    { name: 'I Need Your Love',
      id: 'AtKZKl7Bgu0'}
]}

I want to loop through that array, get the id of each favorite, and do a .find() for that ID in my songs collection of my mongo DB, get the song's artist, and add it to the array.

I've tried something like...

for(var i=0; i<profile.favorites.length; i++) {
    db.songs.find({"_id" : profile.favorites[i].id}, {"artistName" : 1}, function (e, result){
            profile.favorites[i]["artistName"] = result[0].artistName;
        });
    }

But that doesn't seem to working, (primarily because Mongo/MongoJs is async.)

What is the proper way to do something like this?

Answer 1

You can use $in to query an field that match with any value in the specified array.

favoritesId = favorites.map(function(favorite){ return favorite.id; });

db.songs.find({ _id: { $in: favoritesId }}, function(err, songs){
  // do you favor 
});