Push new field and value to json array object in node.js

Question

I'm new to node.js. I need to display Name in jqgrid, but I stored only id of one document into another document.

Example

I have 2 documents like Student master and student mark document. I have to display mark details in jqgrid. In mark document I stored student id instead of name. How do I fetch the name and send a new object to jqgrid?

My code is as follows:

exports.getAllstudentsmark = function(req, callback)
{
    studentsmarks.find(function(error, studentsmarks_collection) {
      if( error ) callback(error)
      else {

        studentsmarks_collection.toArray(function(error, results) {
          if( error ) callback(error)
          else {
            newresult = results;
            for(i=0;i<results.length;i++)
            {
                newresult[i]['studentname'] = getStudentName(results[i].studentid);
            }
            console.log(newresult);
            callback(null, newresult)}
        });
      }
    });
}

var getstudentObjectId = function(id)
{
    return student.db.bson_serializer.ObjectID.createFromHexString(id);
}
var getStudentName = function(id)
{
    student.findOne({_id: getstudentObjectId (id)}, function(e, o){
console.log(o.name);
        return o.name;
    });
}

newresult[i]['studentname'] is always getting undefined. But if I log into getStudentName function I can get answer into getStudentName function.

My callback function is only getting this problem. How to resolve and get my result in an easy way. Please help any one.

Answer 1

try this inside your for loop

newresult.push({'studentname': getStudentName(results[i].studentid) });

exlpanation: by the time you access newresult[i] it doesn't exist, so accessing studentname field of it is impossible

Answer 2

Your problem here is that you are not setting the name of the user into the array, but the return value of student.findOne , since this is an asynchronous method. Maybe try this thing

exports.getAllstudentsmark = function(req, callback)
{
  studentsmarks.find(function(error, studentsmarks_collection) {
  if( error ) callback(error)
  else {

    studentsmarks_collection.toArray(function(error, results) {
      if( error ) callback(error)
      else {
        newresult = [];
        for(i=0;i<results.length;i++)
        {
            getStudentName(results[i].studentid, function (studentName) {
               newresult.push({studentname: studentName});
            })
        }
        console.log(newresult);
        callback(null, newresult)}
    });
  }
});
}

var getstudentObjectId = function(id)
{
    return student.db.bson_serializer.ObjectID.createFromHexString(id);
}
var getStudentName = function(id, callback)

{
    student.findOne({_id: getstudentObjectId (id)}, function(e, o){
console.log(o.name);
        callback(o.name);
    });
}

I hope it helps