Nodejs Mongoose how do I update an object in an array based the objects ID-CodePudding

Here is my an example of a document from my "Cart" schema:

{ 
  _id: 1,
  line_items: [
    { item_id: 101, color: 'white', quantity: 1 },
    { item_id: 101, color: 'green', quantity: 1 },
    { item_id: 102, color: 'white', quantity: 1 },
  ]
}

I want to increase the quantity of the item which is uniquely identified by item_id = 101 and color = 'white'

I want it to be increase by x amount where x can be any number. How do I do this?

(edit 1) Here is what I have tried

await Cart.findById(1).then(doc => {
  const i = doc.line_items.findIndex(elm => { 
    return (elm.item == item && elm.color == color) // (edit 2) item is a variable = 101 and color is a variable = 'white'
  });
  doc.line_items[i].quantity  = quantity;
  doc.save();
}).catch(err => {
  throw err;
});

However, this isnt working because the changes in quantity aren't being saved to the database for some reason even though it is being updated when I console.log() it inside of this code.

I also beleive it should be possible to solve my problem with a single findByIdAndUpdate function though, but I have no idea how to do that

CodePudding user response：

I think you have a problem getting the index. I tried your code and it worked fine.

await Cart.findById
    .findById(1)
    .then((doc) => {
      const i = doc.line_items.findIndex((elm) => {
        //here is elm.item_id
        return elm.item_id == item && elm.color == color;
      });
      doc.line_items[i].quantity  = 10;
      doc.save();
    })
    .catch((err) => {
      throw err;
    });

CodePudding user response：

So apparently the reason my attempt did not work was because doc.save() was not being run because mongoose did not recognize any changes to the document. Why this is the case, I don't know, but by adding the line doc.markModified('line_items'); before saving, it is now working.

await Cart.findById(1).then(doc => {
  const i = doc.line_items.findIndex(elm => { 
    return (elm.item == 101 && elm.color == 'white')
  });
  doc.line_items[i].quantity  = 10;
  doc.markModified('line_items'); // <-- solution
  doc.save();
}).catch(err => {
  throw err;
});