Simplest meaning

A JavaScript library for building user interfaces. It is a javascript library that is used for building user interfaces. 😎

It contains three essential things :

1. Declarative
2. Component-Based
3. Learn Once, Write Anywhere

1. Declarative

• React makes it painless to create interactive UIs.

For example: if we want to add a tag to the other tag so we have to write code like this in javascript

• first, get the id or class name of another tag
• then put the tag in it with the help of innerHTML

but in react we don't need this kind of stuff

• Just create a function like a javascript function
• and return the tag that's it.
• And everything is maintained by the react. Now you have created the component.

2. Component-Based

• Component means dividing the big UI code into the small UI block of code

For example

• let's say we have a home page where have put all the code in it like buttons, navbar, sidebar, body, and so on right.
• Suppose we created a new page like about us where we want to add a button.
• So what we do is just copy the button code from the home page and past it on the about us page
• But there is a problem if we change the color of the button so we have to change the button color on every page

So this problem is resolved by COMPONENT

• Let's take the previous example, how does the component help us to solve this problem?
• First, it creates a separate file like button.js (Component) for the button code Ok

3. Learn Once, Write Anywhere

• this one means reusability
• Right, Now code is more reusable
• we can take the button example create a new button component and put the button code into it.
• And use this component in every file where we want to add button code this is reusable