How to get data from one collection and insert into another collection in Nodejs?

Question

Am using Nodejs and MongoDB and I am new to nodejs. I need to know how to get data from one collection and append some additional data and insert into another collection.

db.collection('collection1').find({ "Id" : 12345 }).toArray(function(err, result){ 
   db.collection('collection2', function(err, collection){
       collection.insert({
          //some data
       })
   })
})

When I try this code its not working its giving me error insert is not defined.

thanks, John.

Answer 1

db.collection('collection1').find({ "Id" : 12345 }).toArray(function(err, result){ 
 //do the modification here 
 db.collection('collection2').insert(modifiedResult, function(err, result){
        if(err) {
            //log error
        }else{
            //log result
        }
    })
})

One more thing, If the result array length is more that one and you want to insert then separately then use promise

db.collection('collection1').find({ "Id" : 12345 }).toArray(function(err, result){ 
 //do the modification here 
  Promise.all(modifiedResult.map((eachModifiedResult)=>{
       return db.collection('collection2').insert(eachModifiedResult);
  }).then((result)=>{
      //result of the insert
  }).catch((err){
     //err if any happen
 });
})

But if you have a very large doc then do it as Neil Said. Read the collection one by one using cursor and modify them and insert them to other db.

Answer 2

You can use callback library like async or Promises Q Promise

var collectionData = null;
var modifiedResult = null;

// here i am using async library to avoid callbackHell

async.series([
    // for get data from collection 1.    
    function(cb) {
        var criteria = {
            "Id": 12345
        }
        db.collection('collection1').find(criteria).toArray(function(dbErr, dbResult) {
            if (err) {
                cb(dbErr)
            } else {
                collectionData = dbResult;
                cb()

            }
        })
    },
    // Append Data in collectionData
    function(cb) {

        // do you work here to append data in collectionData

        modifiedResult = extendedData; // this is just an example you need to work on it 
        cb();

    },
    // Update collection 2 here 
    function(cb) {
        db.collection('collection2').insert(modifiedResult, function(err, result) {
            if (err) {
                cb(dbErr)
            } else {
                collectionData = dbResult;
                cb()

            }
        });
    }

]);