Data is inserting twice in mongodb - node.js

Question

I am reading the json file and check to product document is brand is already there in my document, If for brand suppose multiple products found, Then I am looping through products and check for category in category document. If category does not exist, then I create new document in categories document. But if product found 3 times then new category creating 3 times and respectively. Can anyone help me with this?
Below is my code
jsonData.products.forEach((element, index) => {
//get data from database which have same product
db.Product
.find({ brand: element.brand })
.then(product => {
if (product.length > 0) {
product.forEach((item, productIndex) => {
//Check product title greater than 70 %
// var similarity = stringSimilarity.compareTwoStrings(element.name, item.title);
var similarity = stringSimilarity.compareTwoStrings("surat rawal", "surat rawal prem");
// console.log(element.name, item.title);
if (similarity > 0.7) {
//if categoris found in json file
let newCategory = {};
if (element.categories) {
element.categories.forEach((category, categoryIndex) => {
db.Category
.findOne({
name: category
})
.then(categoryData => {
if (categoryData) {
const categoryObj = item.categories.find(categoryEle => {
return categoryEle.name === categoryData.name;
});
//If category not found on product then add category
if (!categoryObj) {
newCategory.id = categoryData._id;
newCategory.name = categoryData.name;
item.categories.push(newCategory);
}
} else {
//If category is not already there then add new one
const categorySchema = new db.Category({ name: category });
categorySchema
.save()
.then(insertedCategory => {
newCategory.id = insertedCategory._id;
newCategory.name = insertedCategory.name;
item.categories.push(newCategory);
})
.catch(err => {
throw err
})
}
})
.catch(err => console.log(err))
})
}
}
});
}
})
});

Answer 1

A number of observations here:
The section where you call
element.categories.forEach((category, categoryIndex) => {
db.Category.findOne({ name: category })
This is independent from item. You are looking for the categories of element in DB and saving them if they don't exist. So this same piece of code will be executed for each item you found.
Also, remember this:
db.Category.findOne({ name: category })
will be async.
Meaning even if you loop on items, and execute this piece of code, the affect of categorySchema.save() will not reflect. (I assume that's what you were going for here.)
I think the better way to do this would be, just insert all the missing categories without looping over items. After those operations are complete, you can do comparisons with items and make neccesary changes to item.categories (I assume you are going to update back each of the items)