Update JSON variable based on Mongoose results - json

Question

I have a JSON variable outside of mongoDB collection as below
var outputJson = [
{
'Product' : 'TV',
'isSelected': 0
},
{
'Product' : 'Radio',
'isSelected': 0
},
{
'Product' : 'Book',
'isSelected': 0
},
{
'Product' : 'Watch',
'isSelected': 0
}
]
Now I want to update the isSelected key if the product exits in MongoDB; I want something like below
var outputJson = [
{
'Product' : 'TV',
'isSelected': 0
},
{
'Product' : 'Radio',
'isSelected': 1
},
{
'Product' : 'Book',
'isSelected': 0
},
{
'Product' : 'Watch',
'isSelected': 1
}
]
Here is the code that I am trying, but I am not getting the above result
outputJson.forEach(function(key,value){
wishlistData.find({userID:req.user.id}, function(err,data{
data.forEach(function(k,i){
if (data[i].product=== outputJson[value].Product){
outputJson[value].isSelected = 1
}
})
});
})
Any help is appreciated

Answer 1

Firstly, the callback function to forEach is called with the item in the array as the first argument, so data[i] and outputJson[value] are redundant.
You should make use of mongoose's findOne method to see if there's at least one match, and you can pass in Product as follows
outputJson.forEach(function(item) {
wishlistData.findOne({userID: req.user.id, product: item.Product}, function(err, data) {
if (data !== null) { // if it actually found a match
item.isSelected = 1;
}
});
});
But keep in mind that mongoDB queries are asynchronous, so outputJson would still be the same right after the forEach loop. You might want to use promises and Promise.all to ensure that you do stuff with outputJson after all the queries have been processed:
Promise.all(outputJson.map(function(item) {
return wishlistData.findOne({userID: req.user.id, product: item.Product}).then(function(err, data) {
if (data !== null) { // if it actually found a match
item.isSelected = 1;
}
});
})).then(function() {
// do stuff with outputJson here
});

Answer 2

Replace this
if (data[i].product=== outputJson[value].Product){
outputJson[value].isSelected = 1
}
by
if (data[k].product=== outputJson[key].Product){
outputJson[key].isSelected = 1
}
each callback function have first argument as index

Answer 3

First thing, why are you doing the same mongo query repeatedly for each object in the Array, as it will give you the same result. Also use the lodash library 'lodash'. This is how you can achieve this:
var _ = require('lodash')
wishlistData.find({userID:req.user.id}, function (err, data) {
var dataMap = _.indexBy(data, "product");
outputJson.forEach(function(key,value){
if(!_.isEmpty(_.get(dataMap, key.Product))) {
key.isSelected = 1;
}
})
}

Answer 4

Thank you #Ambyjkl, you guidence worked Promise made the trick, I made minor changes to your script and it started working
Promise.all(outputJson.map(function(i,k) {
return wishlistData.findOne({userID: req.user.id, product: i.Product}).then(function(data, err) {
if (data !== null) { // if it actually found a match
i.isSelected = 1;
}
});
})).then(function() {
console.log(outputJson);
});