Node.js Interview Questions and Answers

Fork() is used to spawn a new Node.js process. It invokes a specific module with an IPC communication channel, thus enabling the sending of messages between a parent and child.

Callback hell is a situation in Javascript when you face callbacks within callbacks or nested callbacks.

It looks somewhat like this:

firstFunction(args, function() {
   secondFunction(args, function() {
      thirdFunction(args, function() {
      });
   });
});

There are two significant ways to avoid Callback Hell in NodeJS:

1. Using Promises

const makeBurger = () => {
    return getChicken()
    .then(chicken => cookChicken(chicken))
};
makeBurger().then(burger => serve(burger));

See, it is just more easy to read and manage in comparison to the nested callbacks.

2. Use Async/Await

Using Asynchronous functions, we can convert makeBurger into one synchronous code. Also, maybe you can get helpers to getBun and getChicken at the same time, meaning, you can use await with Promise.all. Here's the code:

const makeBurger = async () => {
    const cookedChicken = await cookChicken(chicken);
    return cookedChicken;
};
makeBurger().then(serve);

Note: Our aim while creating nodejs interview questions, is to help you grow as a Node Developer. The questions mentioned here have been asked by leading organizations during technical rounds of the interview process.

The array of records can easily be bulk inserted into the node.js. Before insertion, you have to convert it into an array of arrays.

• Step1. Install Async first with "npm install async" command
• Step2. Call the async in your file with you will use async.
  var async = require("async");
• Step3. Make an async function and call await function inside async function.
  let phoneChecker = async function (req, res) {
     const result = await phoneExistOrNot();
}
exports.phoneChecker = phoneChecker;

await will work only under async function.
  For example: here is " phoneChecker " is async function, and phoneExistOrNot is await service.
• Step4. Now you can write your logic in await function.
  let phoneExistOrNot = async function (req, res){
    return new Promise(function(resolve, reject) {
        db.query('select name, phone from users where phone = 123456789 ', function (error, result) {
             if(error) {
                 reject(error);
                 console.log('Error');
             } else {
                  resolve(result);
                  console.log('Success');
             }
      })
});
}

A UUID is a Universal Unique Identifier is a method for generating ids that have been standardized by the Open Software Foundation (OSF).

You can generate UUIDs in Node.js through the node-UUID. It is a speedy and straightforward way of generating Version 1 & 4 UUIDs.

Here's how to generate UUIDs

• Install the node-uuid through the npm manager using npm install uuid.
• Use it in your script like this:

const uuidv1 = require('uuid/v1')
const uuidv4 = require('uuid/v4')
var uuid1 = uuidv1()
var uuid5 = uuidv4()

Here is how your output would look. Although, due to the nature of UUIDs, your generated IDs may be completely different.

Output

uuid1 v1 => 6bf958f0-95ed-17e8-sds37-23f5ae311cf6
uuid5 v4 => 356fasda-dad8d-42b7-98b8-a89ab58a645e

If you don't install MySQL then you can install MySQL by npm install mysql.

Tracing is a mechanism in Node.js to provide a centralized tracing information method, which is generated by V8, Node.js core, and the userspace code. It can be enabled with the --trace-event-categories command-line flag or by using the trace_events module.