Modify mongodb records before sending to api response - node.js

Question

I'm using MongoDB as a database and express.js to build API.
I want to modify the response before sending it to the client.
here is my express.js code...
products.route("/:id")
.get((req, res) => {
mdb.get().collection('products').find({_id:parseInt(req.params.id), status:1}).toArray()
.then(response => res.status(200).json(response))
.catch(error => console.error(error));
})
Like, I want to add some calculated filed to the response. suppose my response object from the database is this
response = {
id: 1001,
name: 'Apple',
price: 120
}
Now, I want to add image field. so, my final response object will be
response = {
id: 1001,
name: 'Apple',
price: 120,
image: '/assets/images/'+id+'.jpg'
}
Please help me with this I'm very new in express.js

Answer 1

Inside your router handler, you would do something like this:
Products
.findOneAndUpdate({ _id: req.params._id, status: 1 }, {
$set: {
images: '/assets/images/' + req.params._id + '.jpg'
}
},{
new: true
})
.then(product => {
if(!product) return res.status(404).json("Product not found");
else return res.status(200).json(products);
})
.catch(err => {
console.error(err);
return res.status(500).json(err);
});
Use the findOneAndUpdate method from mongodb on your Products collection to update a document inside that collection.
findOneAndUpdate takes three objects as parameters:
first one specifies the query condition
second specifies the updated document
Here we are using the $set operator to add a image property to the existing document.
third is an options object
set new to true to tell mongo to return the updated document instead of the original one, which is the default
Here is a reference to the docs, for more information: https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndUpdate/
EDIT: To modify the response only, you would do inside the .then:
.then(products => {
const modifiedProducts = products.map(product => ({
...product,
image: '/assets/images/' + product._id + '.jpg'
}));
return res.status(200).json(modifiedProducts);
})
Here we are creating a new object for each product that is being returned, by copying its original contents plus the new image property, then returning that modifiedProducts array to the client