What is Render in React JS? (Basics)

What is Render in React JS– React is a powerful JavaScript library that allows developers to create dynamic user interfaces efficiently. One of its key concepts is rendering, which determines how components appear on the screen. The render() function is at the heart of this process, ensuring that the application updates correctly when data changes.

In this article, we’ll explore what render in React JS is, how it works, its role in class components, and the ReactDOM.render() function. We’ll also include examples, a table comparison, and an FAQ section.

What is Render in React JS?

Rendering in React refers to displaying UI components on the web page. It happens through the render() method in class components or simply by returning JSX in functional components.

What is State in ReactJS?(3+ easy example)

Key Points About Rendering in React:

1. It transforms JSX into real DOM elements.
2. It is a fundamental part of both functional and class components.
3. The render() method is a pure function—it does not modify the state or cause side effects.
4. The ReactDOM.render() function places the React component inside the specified HTML element.

Understanding the render() Method in Class Components

In React class components, the render() method is required. It returns JSX code that tells React what should appear in the UI.

import React, { Component } from 'react';
import ReactDOM from 'react-dom';

class MyComponent extends Component {
  render() {
    return <h1>Hello, React!</h1>;
  }
}

ReactDOM.render(<MyComponent />, document.getElementById('root'));

Explanation

• The render() method returns a simple tag with text.
• ReactDOM.render() takes two arguments: the component and the target DOM element.
• The output is displayed inside the <div id="root"></div> in index.html.

The Role of ReactDOM.render()

The ReactDOM.render() function renders the React component into the specified DOM element.

Syntax

• component: The JSX element or React component to be rendered.
• container: The DOM element where the React component should be inserted.

Example:

ReactDOM.render(<h2>Welcome to React!</h2>, document.getElementById('root'));

This will replace the content inside the root div with the given <h2>tag.

Limitations of the render() Method

While render() is a crucial part of React, it has some limitations:

• Cannot Change State: The render() method is pure and should not modify the state directly.
• No Side Effects: No HTTP requests, timers, or subscriptions should be inside render().
• Returns a Single Element: Must return a single JSX element (can be wrapped in a <div> or React.Fragment).

Table: render() Method vs ReactDOM.render()

Feature	render() Method	ReactDOM.render()
Used In	Class Components	Root Component
Purpose	Returns JSX	Mounts JSX into the DOM
Modifies DOM?	No	Yes
Allows State Change?	No	N/A
Used in Functional Components?	No	Yes

Common Issues with Rendering in React

• Component Not Rendering: Ensure ReactDOM.render() is correctly targeting the HTML element.
• State Not Updating: Use setState() to update state instead of modifying it directly.
• Re-render Loops: Avoid setting the state inside render() to prevent infinite loops.

Conclusion: What is Render in React JS

Rendering is a core concept in React that dictates how UI elements appear on the screen. The render() method in class components returns JSX, while ReactDOM.render() is responsible for mounting React elements into the DOM. Understanding What is Render in React JS and how rendering works ensures efficient and optimized React applications.

FAQs