NodeJS / Mongoose add Subdocument and update total price and quantity-CodePudding

I'm trying to add a subdocument and also update the "total" and "quanity" fields of the main document. Right now, I'm doing it like this, but this seems really ugly and inefficient. Is there a better way to achieve this?

// Adds subdocument    
const cart = await Cart.findByIdAndUpdate({_id: req.session.cart._id}, {$push: {courses: req.body}}, {new:true})

// Update totals and quantity   
cart.set({total: cart.total   parseInt(req.body.price), quantity: cart.quantity   1})
await cart.save()

Ideally I would want something like this (the below clearly doesn't work but it's what I'm aiming for logically):

const cart = await Cart.findByIdAndUpdate(req.session.cart._id, async function(err, doc){
    if(err){
        res.status(404).json({error:err.message})    
    } else{
        doc.courses.push(req.body.course)
        doc.total = doc.total   parseInt(req.body.price)
        doc.quantity = doc.quantity   1
        await doc.save()
       
    }
}, {new: true})

Thank you :)

CodePudding user response：

You can use $inc operator to atomic update one document

refer to $inc operator:

The $inc operator increments a field by a specified value

Your operation could be something like:

const cart = await Cart.findByIdAndUpdate(
  {_id: req.session.cart._id}, 
  {
    $push: {courses: req.body},
    $inc: {
      total: parseInt(req.body.price),
      quantity: 1,
    },
  }, 
  {new:true}
)