Frequently asked MEAN Stack Interview Questions

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Essentially, MEAN stack is an open-source technology that includes four JavaScript-based technologies including MongoDB, ExpressJS, Angular, Node.js (MEAN). By learning and mastering MEAN stack, you can enjoy the perks of a host of domains for developing web apps and dynamic websites.

JS + Nodejs

• Why? What?

• EventLoop

• How single threaded?

• threadpool? Libuv module

• why express?

  • middleware? example

• streams

• event emitter

• how to handle unhandledRejection, uncaughtException

• module.exports vs export

• higher order function

  • callbacks

    • real use case
    • error first callback
    • callback hell ? 1. example 2. how to remove the callback hell

  • promises

    • real use case
    • chaining
    • promiseall vs race vs allSettled

  • async/await

    • real use case

• Hoisting

  • let, var, const, normal funtion
  • why function as expression not hoisted.
  • "use strict"

• null undefined undeclared

• call, apply, bind / context switching

• prototype

• closure

• classes in es5 & es6

• array > filter, map, reduce, foreach, slice, splice

• functions > iffe, expression, normal function

• es6 features

  • fat arrow functions > significance and use
  • classes
  • literal string
  • destructuring object
  • rest and spread operator > significance and use

• Scope in JavaScript > global local lexical

• File system(fs)

  • asynchronous > methods
  • synchronous > methods

• settimeout, setimmediate, setInterval

• cron job

Advance Question

web worker
threads
cluster,fork, process spwan
cors issue > resolution & internal working
virtual dom,real dom,real dom,shadow dom  
scaling

TypeScript

Will Add Soon

Angular

• Angular start point
  purpose index.html and main.ts

• Decorators?

• Module? imports,declaration,providers

• Service?
  @injectable => providedin
  how to make singleton service > 1. providedin="root" & 2.providedin="Module_Name"

• Components?

  • Lifecyclehooks?
    • children method
    • why ngOnchanges called first
    • parameters
    • can we provide service directly in component? how? how many instances created?

• Pipes

  • Custom Pipes ? how to implement and real example
  • Pure pipes

• Directives

  • Types > why component is directive
  • Custom directive ? how to implement and real example

• Can we use *ngIf and *ngFor on single line

• Content projection

• Elvis operator

• Observalables vs promises?

  • why observables are prefered
  • Subjects? Subjects vs BehaviorSubjects vs ReplaySubjects
  • observables chaining

• Interceptor > how to use ? use cases

• Purpose of below files and atleast rough idea of contents

  • package.json & package-lock.json
  • angular.json
  • tsconfig.json

• local storage, session storage and cookies

• Karma & Jasmine? describe, it, Spyon, Spy, beforeEach, expect

• Event binding & Property binding

• Event bubbling

  • how to stop propagation vs prevent default
  • event delegation

• Url/dom sanitization

• Share data between component methods > total 5 method (state any 2-4)

• ng-container vs ng-template

• Security features in your application

• Change detection

  • ngzone
  • which component lifecyclehook called

• Routing

  • purpose of base href tag
  • lazy loading > what it is? how to implement
  • router outlet, router links, router state, routerLinkActive
  • Wildcard route
  • Route Guards > Methods and purpose (CanActivate, CanActivateChild, CanDeactivate,Resolve and CanLoad)

• Just-in-Time (JIT) vs Ahead-of-Time (AOT)

• rxjs, rxjs operators with example

Mongodb

Why mongoose? > any other orm  
	find  
aggregate > stages  
	joins($loookup) > foreign key, left outer join only  
	optimization  
replica  
sharding  
cluster  

JWT

Why?  
   (rough idea) how it works  
methods > use  
bcrypt vs jwt  
drawbacks

RestApi

Why?  What?  

Programs

string reverse (using inbuilt methods and by loop) 1. simple 2. sentence( normal, word by word reverse)  
string manipulation (using inbuilt methods and by loop)  
fibonacci series (using recursion and loop) 1. simple 2. till n terms  
palindrome(string and number)  
factorial of number (small number and big number)  
array (sort, find,remove duplicates, replace value, reverse, find 2nd highest number)  
prime number( single number, range, next of given number)
let var const  
0.1+0.2==0.3 (reason why not equal)  
console.log(3>2>1)	console.log(1<2<3)  
console.log(1 ?? 3)  
methods for creating object & object cloning(shallow & deep) with example