01 Basics - biswajitsundara/react GitHub Wiki

React is a client side JavaScript library that helps to build modern reactive user interfaces for web.

React is an UI library created by Facebook
React follows component based architecture (UI components)
Basically we build custom HTML elements using React
React is declarative (say what to do without explicitly specifying each instruction)

Components

Components are independent and reusable block of code.
This is similar to Java script function however works in isolation and returns HTML.
A component is mainly consists of HTML + CSS + JS
The advantage of using component architecture is - Reusability & Separate Concerns

Component Tree

React & ReactDOM

React & react dom are two libraries that we are going to work
We write all the codes in javascript
index.js file is the first to execute

Imperative vs Declarative

In imperative approach we give each and every instruction to the DOM
Vanilla javascript is an imperative approach.

<html>
   <body id="root">
       <script>
            const para = document.createElement('p');
            para.textContent = 'This is visible';
            document.getElementById('root').append(para);
       </script>
    </body>
</html>

But in react, it will be declarative approach
We need to specify what do we want on the screen
And react will generate the instructions.

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