Regarding storing complex datas, and retreiving complex datas using node.js and mongodb

I am trying to store a task into mongodb such as simple adding like 1+1, or a list of questions, but so far I only got to store simple data such as a string, I have some idea regarding how database work conceptually, but is new to actually implementing a database operation, so if anyone can give me some hints regarding to this issue it would be much appreciated. Thanks in advance

var Task = new Schema({
  task: String
});

var Task = mongoose.model('Task', Task);

var app = module.exports = express.createServer();


app.put('/tasks/:id', function(req, res){
  Task.findById(req.params.id, function (err, doc){
    doc.updated_at = new Date();
    doc.task = req.body.task.task;
    doc.save(function(err) {
      if (!err){
        res.redirect('/tasks');
      }
      else {
        // error handling
     }
   });
  });