为mongoose执行find()时找到的每个文档执行回调

I have:

我有:

Emotion.find (query, "-_id", opts, function (error, e){
    if (error) return cb (error, 500);
    for (var i=0, len=e.length; i<len; i++){
        e[i] = convert (e[i]);
    }
    cb (null, e);
});
Emotion.find (query, "-_id", op