What is ReactJS? Simple introduction with ReactJS

Habibullah Bahar Piash
2 min readMay 7, 2021

What is React JS?

React is basically an open-source, javascript library for building user interfaces especially for Single Page Applications.

React is a library, not a framework

React is not exactly a “framework”. It is not a complete solution and you will often need to use more libraries with React to form any solution. React does not assume anything about the other parts in any solution.

React uses JSX

JSX stands for JavaScript XML. React uses JSX instead of using regular JavaScript. JSX allows us to write HTML in React.

You are not required to use JSX, but JSX makes it easier to write React applications.

Virtual DOM

React creates an in-memory data structure cache(a reserved storage location that collects temporary data to help websites, browsers, and apps load faster) which computes the changes made and then updates the browser. This allows a special feature that enables the programmer to code as if the whole page is rendered on each change whereas React library only renders components that actually change.

React is all about components

In React, we describe UIs using components that are reusable, composable, and stateful.

We define small components and then put them together to form bigger ones. All components small or big are reusable, even across different projects.

You can think of components as simple functions (in any programming language). We call functions with some input and they give us some output. We can reuse functions as needed and compose bigger functions from smaller ones.



Habibullah Bahar Piash

Web Design & Development is my passion! I love to learn and explore new tech things.