How to increase or decrease quantity in node.js?-CodePudding

      app.put('/product/:id', async(req, res) =>{
        const id = req.params.id;
        const updateQuantity = req.body;
        const filter = {_id: ObjectId(id)};
        const options = { upsert: true};
        const updateDoc = {
            $set: {
                productQuantity: updateQuantity.productQuantity
            }
        };
        const result = await productCollection.updateOne(filter, updateDoc, options);
        res.send(result);

    })

//this code only can replace the quantity can't increase or decrease the quantity.

CodePudding user response：

You can try the increment operator $inc along with findOneAndUpdate. The code would change as follows:

app.put('/product/:id', async (req, res) => {
    const id = req.params.id;
    const updateQuantity = req.body;
    const filter = { _id: ObjectId(id) };
    const options = { upsert: true };
    const updateDoc = {$inc : {'productQuantity' : 1}};
    const result = await productCollection.findOneAndUpdate(filter, updateDoc, options).exec()
    res.send(result);
});

To decrease the value: const updateDoc = {$inc : {'productQuantity' : -1}};

CodePudding user response：

To increase the count by 5.

const updateDoc ={
    $inc: {
        productQuantity: 5
    }
};

To Decrement the count by 5

const updateDoc ={
    $inc: {
        productQuantity: -5
    }
};

Now make sure the value passed to the productQuantity is a Number and not a string. You can do that by passing updateQuantity.productQuantity in Number constructor like


const productQuantity = Number(updateQuantity.productQuantity)

// increment
const updateDoc ={
    $inc: {
        productQuantity: productQuantity,
    }
};

// decrement
const updateDoc ={
    $inc: {
        productQuantity: productQuantity * -1
    }
};

PS: product.productQuantity is a bad name. Try product.quanlity next time.