React is a library of JavaScript. It is not like Angular framework It doesn’t help with server communication, translations, routing. React is thin and it’s extremely easy to mix it with other 3rd party libraries. React use JSX syntax. It is declarative. In React use declarative style to write components. In React make HTML, JS and often CSS together as a component.


JSX is a syntax extension to JavaScript. It using with React to describe what the UI should look like. JSX may remind you of a template language, but it comes with the full power of JavaScript…

JavaScript Types

Number, String , Boolean, Symbol , Object , Null, Undefine.

Object are 4 types.

Function, Array , Date, RegExp.


In JS numbers are double precision 64 bit. String can convert in Int using parseInt() function.

Its first parameter is string, second base. Base is optional .But some times it give wrong value without base . parseFloat() function convert string to float. Difference between parseInt() and parseFloat() is parseFloat ( ) take base 10 all time.


numeric operator are +, -, *, / & %.Compound assignment statements such as += and -=. Increment and decrement operator is ++ and…

What is a web server?

On the hardware side, a web server is a computer that stores web server software and a website’s component files. (for example, HTML documents, images, CSS stylesheets, and JavaScript files). Web server connects to the Internet. On the software side, a web server includes several parts that control how web users access hosted files. An HTTP server is a software that understands URLs(web addresses). An HTTP server sends the URL to DNS. A Domain Name Server (DNS) converts this URL to an IP Address which in turn points to a Web Server. All websites on…


Closures are a fundamental concept in JavaScript. When a function is able to remember and access its scope even when that function is execute outside its scope its closures.

React Hooks

Hook is a special function in React features. If a function component add some state to it, a Hook inside the existing function component. React Hooks are a new addition in React 16.8. It define without writing a class. Hooks define top of the function.

Its helps developer to write extra code. Its reduce complexity form code.

useState Hook

This hook use to set the value of a…


Type of Value

There are mainly 2 type JavaScript value. Primitive and other are Object & Function. In Primitive value there are nine types.

Primitive Type Value

Undefined​, Null​, Booleans​, Numbers​, Strings​, Symbols​, BigInts

Object and Function:

console.log({}) //object type

console.log([]) // object type

console.log(x=>x+4) // function type

Check Type:

In JavaScript can check the value type using typeof() expression. If we give any expression JavaScript return the value as string as like “number”, “string”, “object” etc. type the example and the see the result.

console.log(typeof(2)) //”number”

console.log(typeof(“hello”)) //”string”

console.log(typeof([])) //”object”

console.log(typeof({})) //”object”

try … catch

In JavaScript code…

Nandita Mandal

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