Hi, I am Emon. A professional web developer. In this blog, I will talk about the 10 most important javaScript interview questions. So let’s start ……

1. What are the differences between == and === ?

Answer: == in JavaScript is used for comparing two variables, but it ignores the data type of variable. === is used for comparing two variables, but this operator also checks datatype and compares two values.

2. What are the differences between null and undefined?

Answer: In javascript undefined means variable declared but the value has not yet been assigned. There are many ways have to find undefined.

let fun = undifine;
console.log(fun); // undifine
Example: 2
let name;
console.log(name); // undifine

In this blog, we are learning about react core concepts. React is a JavaScript library. React makes User Interfaces (UI). User Interface (UI) means what we see in the browser as a user. UIs are everywhere.

The React language

In the below for example we declare an array

const users = [
{ name: 'Emon', age: 21},
{ name: 'Rana', age: 19},
{ name: 'Iftekhar', age: 23},

This users array is the starting state of your UI. If you want to display them and manage them at first you need to build a UI.

<header>User List</header><ul>
{users.map(user =>…

JavaScript is a single-threaded non-blocking asynchronous language. It works asynchronously.


console.log("Hello World!")setTimeOut(() => {
console.log("I am Emon")
}, 1000)
console.log("A web developer")// Output is:
Hello World
A web developer
I am Emon

# Primitive Values in javaScript:

primitive value can be a number, string, boolean, symbol, and other things.All primitives are constant, they cannot be altered.

console.log('hello world');

# OPP in javaScript:

OPP means object-oriented programming. It’s called syntactic sugar.

class Person{
constructor(firstName, lastName){
this.firstName = firstName;
this.lastName = lastName;

getFullName() {
return this.firstName + " " + this.lastName;
const person1 = new Person('Emon' , 'Hossain');
console.log(person1) …

What is JavaScript: JavaScript is a dynamic computer programming language. It is lightweight and most commonly used as a part of web pages, whose implementations allow client-side script to interact with the user and make dynamic pages. It is an interpreted programming language with object-oriented capabilities.

1. Variables

A Variable that stores any data. It should be an object, an array, number, string. Variables Can be expressed in three ways. These are var, let, and const.


Var name = 'Emon';
let passion = 'programming';
const age = 20;

The top three things are variables. They are storing data. If I now…

Mohhammad Emon

React Developer || JavaScript Developer || MERN Stack

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store