Finding a nested document and pushing a document into a nested document - mongodb

Question

So i started learning mongoDB and moongoose today. I have the following Schema:
{
username: {
type : String,
required : true,
unique: true,
trim : true
},
routines : {
type: [
{
_id : mongoose.Schema.Types.ObjectId,
name : String,
todos : [
{
_id : mongoose.Schema.Types.ObjectId,
todo : String,
isCompleted : Boolean
}
]
}
],
}
}
for example:
{
"username": "John",
"routines": [
{
"_id" : 1234, //just for an example assume it to be as 1234
"name" : "Trip plan",
"todos" : [
{
"_id": 1213123,
"todo": "book flight",
"isCompleted" : "false"
}....
]
}......
]
}
what i want to do is, first i would select a document from collection, by using username, then in routines(Array of objects), i want to select a particular routine by id, which would be given by user in request body, now in the selected routine, i want to push into todos array.
For above example, suppose, selecting document with username john, then selecting an object from routines array with _id as 1234, then to its todos i will add a todo.
I have spent almost a day searching about how to do this, while doing this i learnt concepts like arrayFilters, projections. But still couldn't get how to do. Also i read many answers in Stack Overflow, i couldn't grasp much out of them.
PS:I am very new to MongoDB and mongoose, Chances that my question is very silly, and might not be good as per stack overflow standards, I apologize for the same.

Answer 1

You were on the right track, you indeed want to use arrayFilter to achieve this.
Here is a quick example:
// the user you want.
let user = user;
await db.routines.updateOne(
{
username: user.username
},
{
$addToSet: {
"routines.$[elem].todos": newTodo
}
},
{arrayFilters: [{'elem._id': "1234"}]}
);