Express JS Interview Questions And Answers

Q: What is NodeJS?

Node.js is a particularly powerful framework developed on Chrome’s V8 JavaScript engine that compiles the JavaScript directly into the native machine language. it's a lightweight framework used for creating server-side web applications and extends JavaScript API to supply usual server-side functionalities. it's generally used for large-scale application development, especially for video streaming sites, single-page applications, and other web applications.

Q: In which Language Node JS is written?

Node js is written in C, C++,JavaScript. It used Google’s open-source V8 Javascript Engine to convert Javascript code to C++.

Q: How are you able to avoid callback hells?

There are many ways to unravel the difficulty of callback hells:

  1. modularization: break callbacks into independent functions,
  2. use an impact flow library, like async.
  3. use generators with Promises,
  4. use async/await (note that it's only available within the latest v7 release and not within the LTS version.

Q: Where Node.js are often used?

  • Node.js are often wont to develop:
  • Real-Time Web Applications
  • Network Applications
  • Distributed Systems
  • General Purpose Applications

Q: What's Scaffolding in Express.js?

Scaffolding is creating the skeleton structure of the appliance

There are 2 thanks to doing this:

  • Express application generator
  • Yeoman

Q: Explain REPL within the context of Node.js.

REPL in Node.js stands for reading, Eval, Print, and Loop. It represents a computer environment like a Windows console or Unix/Linux shell where any command is often entered then the system can respond with an output. Node.js comes package with a REPL environment by default. REPL can perform the below-listed tasks.

Q: What are the various API functions supported by Node.js?

There are two sorts of API functions. they're as follows:

  • Synchronous APIs: Used for non-blocking functions
  • Asynchronous APIs: Used for blocking functions

Q: Explain Modules in Node JS?

Modules are reusable blocks of code whose existence doesn't impact other code in any way. it's not supported by Javascript. Modules are introduced in ES6. Modules are very important for Maintainability, Reusability, and Namespacing of Code.

Q: List down the main security implementations within Node.js?

Major security implementations in Node.js are:

  • Authentications
  • Error Handling

Q: What's Middleware is Express.js?

  • Middleware may be a function that's invoked by the Express routing layer before the ultimate request handler.
  • Middleware functions can perform the subsequent tasks:
  • Execute any code.
  • Make changes to the request and therefore the response objects.
  • End the request-response cycle.

Q: Call subsequent middleware functions within the stack.

If the present middleware function doesn't end the request-response cycle, it must call next() to pass control to the subsequent middleware function. Otherwise, the request is going to be left hanging.

Type of Middleware:

  • Application-level middleware
  • Router-level middleware
  • Error-handling middleware
  • Built-in middleware
  • Third-party middleware

Q: Database integration in Express.js?

Adding the potential to attach databases to precise apps is simply a matter of loading an appropriate Node.js driver for the database in your app

Express.js supports many RDBMS & NoSQL Database like

  • MongoDB
  • MySQL
  • Oracle
  • PostgreSQL
  • SQL Server
  • SQLite

Q: What is Package.json?

package.json is present within the root directory of any Node application/module and is employed to define the properties of a package.

Q: What does one understand by ESLint?

ES Lint is an open-source project firstly developed by Nicholas C. Zakas in 2013 which aims to supply a linting utility for JavaScript through a plug. Linters in Node.js are good tools for searching certain bug classes, especially those which are associated with the variable scope.

Also Read: Top Web Designer Interview Questions And Answers