Express and Node JS Interview Questions

Express and Node JS Interview Questions Download Express and Node JS Interview Questions PDF

Express and Node JS Interview Questions

Express.js is a lightweight web application which helps in organizing the web application into MVC architecture on the server side.

V8 is Google’s open source high-performance JavaScript engine, written in C++ and used in Google Chrome, the open source browser from Google, and in Node.js, among others. It implements ECMAScript as specified in ECMA-262, and runs on Windows 7 or later, macOS 10.5+, and Linux systems that use IA-32, ARM, or MIPS processors. V8 can run standalone or can be embedded into any C++ application.

There is no notion of any database in Express JS. So, the concept of models is left up to third-party node modules, allowing the users to interface with nearly any type of database.

There’s no need to render HTML with the res.render () function. If there’s a specific file, then you should use the res.sendFile () function. If any assets are being served from a dictionary, then express.static () middleware function needs to be used.

Below are the few reasons why to use Express with Node.js

  • Express js is built on top of Node.js. It is the perfect framework for ultra-fast Input / Output.
  • Cross Platform
  • Support MVC Design pattern
  • Support of NoSQL databases out of the box.
  • Multiple templating engine support i.e. Jade or EJS which reduces the amount of HTML code you have to write for a page.
  • Support Middleware, basic web-server creation, and easy routing tools.
CLI stands for Command Line Interface. It is a utility or program on your computer where users type commands to perform some action or run some script rather than clicking on the screen.
There are different types of command line interfaces depending on which operating system you are using. We have listed some of them below.
  • Bash on Linux.
  • Terminal of Mac.
  • Command Prompt or Powershell on Windows
  • Shell/ Command line/terminal on Unix and Ubuntu

In Node Js all core modules, as well as most of the community-published modules, follows a pattern where the first argument to any callback handler is an error object. this object is optional, if there is no error then in that case null or undefined is passed to the callback.

Example of the callback function

function callback(err, results) {
	// usually we'll check for the error before handling results
	if(err) {
		// handle error somehow and return
		// no error, perform standard callback handling

Using Node Js you can build applications like:

  • Internet of Things
  • Real-Time Chats Applications
  • Complex Single-Page Applications
  • Real-Time Collaboration Tools
  • Streaming apps
  • Microservices / API’s

Following are the steps used to set up an express JS application: –

  1. A folder with the same name as the project name is created.
  2. A file named package.json is created inside the folder created.
  3. “npm install” command is run on the command prompt. It installs all the libraries present in package.json.
  4. A file named server.js is created.
  5. “Router” file is created inside the package which consists of a folder named index.js.
  6. “App” is created inside the package which has the index.html file.

This way, an express JS application is set up.

Yes, Node Js is single threaded to perform asynchronous processing. Doing async processing on a single thread could provide more performance and scalability under typical web loads than the typical thread-based implementation.

The main difference between the put and the patch is

The embedded entity is believed to the modified version of the resources that are deposited on the original server. It is requested to the client to replace the stored is substituted.In this, the information regarding the way of modifying the original server which has the resources to produce a new version is found.
At the time of updating the resource, you need to forward full payload as the request.At the time of updating the resource, you only need to send the parameter of the resource which you want to update.

Since authentication is an opinionated area which is not ventured by express JS, therefore any authentication scheme can be used in express JS for the authentication of users.

Streams are special types of objects in Node that allow us to read data from a source or write data to a destination continuously. There are 4 types of streams available in Node Js, they are

  • Readable − For reading operation.
  • Writable − For writing operation.
  • Duplex − Used for both read and write operation.
  • Transform − A type of duplex stream where the output is computed based on the input.

Further reading:

Express JS supports any template engine that conforms to the (path, locals, callback) signature.