使用 Mongoose 从对象数组中获取和操作键的值

Question

This is a document from my profiles collection:

{
    _id: ObjectId("5f2ba3a43feccd0004b8698c")
    userID: "238906554584137728",
    serverID: "533691583845892100",
    username: "W.M.K",
    money: 15775,
    __v: 4,
    items: [...],
    serverName: "W-15i: Overworld",
    gladium: 7959.33,
    stocks: [{
        _id: {...},
        stockID: "605b26d309a48348e05d88c9",
        name: "GOOGL",
        amount: 1,
        desc: "Alphabet Inc's (Google) Stock."
    }]
}

I'm using const profile = await Profile.findOne({userID: userID, 'stocks.stockName': stock.name})

EDIT: For one stock, it's as easy as profile.stocks[0].amount -=1 . But when I have multiple stocks, how do I get the amount and manipulate it like amount -= 1 ?

Answer 1

there are few ways you can go through an array of objects in mongoose... you can map through the array, you can also use dot notation in an update. Either way one thing you'll need to do is mark the document modified because mongo doesn't detect changes in arrays of objects. To do this, make the changes and then use the markModified() function on the document. It takes a parameter of the array field name that was modified. in this case.... profile.markModified('stocks')

This is done after changes and before the save.

You can use dot notation with mongoose and you can also iterate through the array via map or forEach

The benefit of using map is that you can double it up with.filter() to filter the array for certain stocks

Answer 2

As already stated by Jeremy, it is basically a matter of array manipulations. Here is one example:

for(let i = 0; i < profile.stocks.length; i++) { 
 profile.stocks[i].amount -= 1;
}

If you just want to update the profile on your database, you could also look into some very advanced mongodb querys (I think it's called "aggregation"), but that is probably overkill.