Node.js Data-Completion script

Question

Following task:

Customer-data, given in a JSON-file, have to be completed with additional address-data. Given in a second JSON-file.

Then these data-stock has to be saved into a MongoDB-database.

Schema of the customer-JSON:

[
 {
 "id": "1",
 "first_name": "Ario",
 "last_name": "Noteyoung",
 "email": "[email protected]",
 "gender": "Male",
 "ip_address": "99.5.160.227",
 "ssn": "509-86-9654",
 "credit_card": "5602256742685208",
 "bitcoin": "179BsXQkUuC6NKYNsQkdmKQKbMBPmJtEHB",
 "street_address": "0227 Kropf Court"
 },
 {
 "id": "2",
 "first_name": "Minni",
 "last_name": "Endon",
 "email": "[email protected]",
 "gender": "Female",
 "ip_address": "213.62.229.103",
 "ssn": "765-11-9543",
 "credit_card": "67613037902735554",
 "bitcoin": "135wbMcR98R6hqqWgEJXHZHcanQKGRPwE1",
 "street_address": "90 Sutteridge Way"
 },
... 
]

Schema of the addresses-JSON:

[
 {
 "country": "United States",
 "city": "New Orleans",
 "state": "Louisiana",
 "phone": "504-981-8641"
 },
 {
 "country": "United States",
 "city": "New York City",
 "state": "New York",
 "phone": "212-312-1945"
 },
...
]

Desired result:

[
 {
 "_id" : ObjectId("5b3f16f5743a6704739bf436"),
 "id" : "1",
 "first_name" : "Ario",
 "last_name" : "Noteyoung",
 "email" : "[email protected]",
 "gender" : "Male",
 "ip_address" : "99.5.160.227",
 "ssn" : "509-86-9654",
 "credit_card" : "5602256742685208",
 "bitcoin" : "179BsXQkUuC6NKYNsQkdmKQKbMBPmJtEHB",
 "street_address" : "0227 Kropf Court",
 "country" : "United States",
 "city" : "New Orleans",
 "state" : "Louisiana",
 "phone" : "504-981-8641"
 },
 ...
]

My solution:

const mongodb = require("mongodb");
const filePathCustomer = "./customers.json";
const filePathAddresses = "./addresses.json";
const MongoClient = mongodb.MongoClient;
completeCustomers = (filePathCustomers, filePathAddresses) => {
 const customers = require(filePathCustomers);
 const addresses = require(filePathAddresses);
 return (updatedCustomers = customers.map((customer, index) => {
 const updatedCustomer = Object.assign(customer, addresses[index]);
 return updatedCustomer;
 }));
};
MongoClient.connect(
 "mongodb://localhost:27017/bitcoinExchange",
 (error, client) => {
 if (error) {
 throw new Error("Connecting to MongoDb has failed.");
 }
 const db = client.db();
 let execCompleteCustomer = new Promise(resolve => {
 resolve(completeCustomers(filePathCustomer, filePathAddresses));
 });
 execCompleteCustomer
 .then(customer => {
 db.collection("customers").insertMany(customer, (error, result) => {
 if (error) {
 db.close();
 throw new Error("Writing to database has failed");
 }
 console.log(
 "Count of customer documents inserted:",
 result.insertedCount
 );
 return true;
 });
 })
 .then(result => {
 if (result) db.close();
 })
 .catch(() => {
 db.close();
 throw new Error("The merging of the customer-data has failed.");
 });
 }
);

What would you have done different and why?

Is my error-handling done in a good way and fashion? How could it be improved?

What bothers me a bit are this multiple occurences of db.close().

Is there a way in Node to avoid these redundancy?

Something like finally in Java.

• Mast: How do you know which address to couple with which customer? They don't share an identifier and relying on the order in a JSON smells like a bad idea.
• michael.zech: It's exactly the same amount of objects in addresses then in customer. The element n in customer maps to the element n in addresses. E.g.: customer[3] maps to addresses[3] and so on ...

Answer 1

Just a few things

1. To start out, the return statement in your function completeCustomers should/could be changed.

The way the function is defined should also be changed. But we'll get to that in a second.

return (updatedCustomers = customers.map((customer, index) => {
 const updatedCustomer = Object.assign(customer, addresses[index]);
 return updatedCustomer;
}));

I would replace with:

return (updatedCustomers = customers.map((customer, index) => ({
 ...customer,
 ...addresses[index]
})))

Note, you don't have to make it take up multiple lines if you don't want.

2. Use const when you don't modify a variable, or arrow function

This means that the two functions below need to change:

completeCustomers = (filePathCustomers, filePathAddresses) => {

Would become:

const completeCustomers = (filePathCustomers, filePathAddresses) => {

---

let execCompleteCustomer = new Promise(resolve => {

And this would become:

const execCompleteCustomer = new Promise(resolve => {

That's all I have for now, but I'm not getting what part you are saying is redundant. And I think you handled the errors well.