Express Response: Sending an Array as JSON - arrays

Question

I'm having an issue trying to get data from my backend express api. I'm using mongodb and mongoose too. Here's my code:
Code:
const show = (req, res) => {
const product = {}
product.array = new Array()
console.log(req.cart.product[1])
for (let i = 0; i < req.cart.product.length; i++) {
Product.find({_id: ObjectId(req.cart.product[i])},function(err,products){
if (err) {
res.sendStatus(500)
} else {
product.array.push(products)
console.log(product.array)
}
})
}
req.cart.product = product.array
res.json({
cart: req.cart.toJSON({ virtuals: true, user: req.user })
})
}
Console.logs:
[ [ { _id: 5952b57ea52d092b8d34c6b0,
name: 'test00000',
price: 0,
description: 'test',
__v: 0 } ] ]
[ [ { _id: 5952b57ea52d092b8d34c6b0,
name: 'test00000',
price: 0,
description: 'test',
__v: 0 } ],
[ { _id: 5952b57ea52d092b8d34c6b0,
name: 'test00000',
price: 0,
description: 'test',
__v: 0 } ] ]
URL Response:
{
"cart": {
"_id": "5953b153d2108941d15a7fe9",
"updatedAt": "2017-06-28T13:38:27.406Z",
"createdAt": "2017-06-28T13:38:27.406Z",
"owner": "595153ad6f18427ef38c416b",
"__v": 0,
"product": [],
"id": "5953b153d2108941d15a7fe9",
"editable": false
}
}
Everything in the console logs is what I want to return in the products array for my response but it won't populate the array when I push it. Any thoughts?

Answer 1

You are trying to call asynchronous code, (e.g. Db query) inside the synchronous code (e.g. for-loop). That's why it returns data to client once it gets the data for the first time. You can async or promise.all to solve the problem.
var async = require('async')
const show = (req, res) => {
const product = {}
product.array = new Array()
console.log(req.cart.product[1])
async.each(req.cart.product, function(id, cb){
Product.find({_id: ObjectId(id)},function(err,products){
if (err) {
cb(err)
} else {
product.array.push(products)
console.log(product.array)
cb()
}
})
}, function(err){
if (err) {
return res.sendStatus(500)
} else {
req.cart.product = product.array
return res.json({
cart: req.cart.toJSON({ virtuals: true, user: req.user })
})
}
})
}
Promise based solution:
const show = (req, res) => {
const product = {}
product.array = new Array()
console.log(req.cart.product[1])
const promises = []
req.cart.product.forEach(function(id){
promises.push(Product.find({_id: ObjectId(req.cart.product[i])}))
})
Promise.all(req.cart.product.map(function(id) {
return Product.find({_id: ObjectId(id)})
})).then(function(products){
req.cart.product = product.array
return res.json({
cart: req.cart.toJSON({ virtuals: true, user: req.user })
})
}).catch(function(err){
return res.sendStatus(500)
})
}