The code is as follows. In fact, I feel that the writing is not elegant at all...

var aDocs ,bDocs =null ;
aModel.find({ user_id:xx , file_name:xx , page_id:xx})
    .then(function(docs){
        aDocs = docs;
        return bModel.find({ user_id:xx , file_name:xx , page_id:xx}) })
    .then(function(docs){
        bDocs = docs ;
        other codes
    })

If you need them to execute concurrently, you can use Promise

const query1 = aModel.find(query)
const query2 = bModel.find(query)
Promise.all([query1, query2]).then(rs => {})

If you don’t need to do it concurrently and can do it synchronously, you can use yield or async/await

const query1 = yield aModel.find(query)
const query2 = yield bModel.find(query)

// 需要node7以上
const query1 = await aModel.find(query)
const query2 = await bModel.find(query)

Of course the upstairs is not very elegant. What you need is async/await, so upgrade node to 7.6 or above

Really? Doesn't the mongoose api have a method for multi-table query?