JavaScript, Crack the Interview

Equality Operators

'1'  ==  1         // true
1 == '1' // true
0 == false // true
0 == null // false
3 === 3   // true
3 === '3' // false


  • accessing the global variable undefined
  • accessing a declared but not yet initialized variable
  • calling functions without a return statement
  • return with nothing to return
  • non-existent object properties
  • function parameters without any explicit value
var name; 
var name; 
console.log(typeof (name));


console.log(typeof (null));


a = 5;
console.log(a); // Error
b = 5;
console.log(b); // 5
var b;

Object Oriented Programming

  1. Encapsulation
  2. Polymorphism
  3. Inheritance

Call Stack

function firstFunction(){
throw new Error('Stack Trace Error');
function secondFunction(){
function thirdFunction(){
//Stack Trace Error! But it also represents the corresponding call //stack
// at firstFunction (<anonymous>:2:11)
// at secondFunction (<anonymous>:5:5)
// at thirdFunction (<anonymous>:8:5)
// at <anonymous>:10:1

Higher-Order Functions

const numbers = [1,2,3,4,5];
const total = numbers.reduce((a,b)=>a+b,0);
console.log(total) // 15

JavaScript Scope

  • Local scope
  • Global scope





I am Sakib Uddin from Bangladesh. I am a front End Developer

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I am Sakib Uddin from Bangladesh. I am a front End Developer

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