Update existing items in nested array using mongoose - node.js

Question

There is a schema as mentioned below. I'm trying to update the existing todo.task.
The problem is, I am storing the path as var done = 'todos.'+todoIndex+'.tasks.'+taskIndex+'.done' and it does not work. I was looking to update like todos.0.tasks.0.done:req.body.done, but it doen't work at all.
(todoIndex and taskIndex are in string which stores the index values)
What is the correct way of doing this?
var mongoose = require('mongoose');
var todoSchema = {
authorId : mongoose.Schema.Types.ObjectId,
date:{
type:Date
},
title : {
type : String
},
description : {
type : String
},
todos : [ {
created : {
type : Date
},
updated : {
type : Date
},
title : {
type : String
},
description : {
type : String
},
done:{
type:Boolean
},
deadline:{
type:Date
},
tasks : [ {
done : Boolean,
task : String
} ]
} ]
}
module.exports = new mongoose.Schema(todoSchema);
module.exports.todoSchema = todoSchema;
I was trying to build the Api like this:
api.put('/notebooks/todo/update/:pid',wagner.invoke(function(Todo,User){
return function(req,res){
var taskIndex=req.body.taskIndex;
var todoIndex=req.body.todoIndex;
var done = 'todos.'+todoIndex+'.tasks.'+taskIndex+'.done';
console.log(done);
Todo.update({_id:req.params.pid},{$set:{
done : req.body.done,
}}, function(err,done){
console.log( done);
})
}}));

Answer 1

If you're using a recent Node version, you can use a computed property name:
Todo.update({ _id : req.params.pid }, { $set : { [ done ] : req.body.done } }, ...
Otherwise, you need to use an intermediate object:
var done = 'todos.'+todoIndex+'.tasks.'+taskIndex+'.done';
var obj = {};
obj[done] = req.body.done;
Todo.update({ _id : req.params.pid }, { $set : obj }, ...