Virtual DOM in React

How React Works with Virtual DOM - Step-by-Step

• Initial DOM State: React creates an initial virtual DOM, which is a lightweight copy of the real DOM.
• State Change: When a component's state changes, React updates the virtual DOM first.
• Comparison: React compares the updated virtual DOM with the previous version to find differences (known as the "diffing" process).
• Reconciliation: React then updates only the changed components in the actual DOM, rather than re-rendering the entire DOM.
• Efficient Update: The actual DOM is updated with minimal changes, ensuring faster and more efficient re-rendering.

Example:

1. Initial DOM State:

<div>
    <div>
        <h1>Welcome to Coding Ninjas Studio!</h1>
    </div>
    <div>
        <h1>Welcome Again!</h1>
    </div>
</div>

2. Updated DOM State:

<div>
    <div>
        <h1>Welcome to Coding Ninjas Studio!</h1>
    </div>
    <div>
        <h1>This is the Updated DOM State.</h1>
    </div>
</div>

React efficiently updates only the changed content (the second <h1> tag in this case) by comparing the virtual DOM with the real DOM and updating only the necessary parts.

What is the Virtual DOM in ReactJS?

The Virtual DOM in ReactJS is a lightweight in-memory representation of the real DOM. When a component’s state changes, React updates the Virtual DOM first. It then compares the updated Virtual DOM with the previous one using a process called "diffing" to identify changes. Only the changed parts of the actual DOM are updated, improving performance by minimizing unnecessary re-renders. This ensures faster updates and a more responsive user interface.

How to Make Things Faster with Virtual DOM in React?

React's virtual DOM improves performance by optimizing how changes are applied to the DOM. When a component's state or props change, React constructs a new virtual DOM tree and compares it with the previous one. It then identifies the differences (known as "diffing") and updates only the affected parts of the actual DOM. This approach reduces the number of expensive DOM operations, resulting in faster rendering and improved application responsiveness. Additionally, React's reconciliation process intelligently handles updates, ensuring that only necessary changes are applied, further enhancing performance.

Features of Virtual DOM in React

The Virtual DOM in React offers several key features that improve performance and enhance the user experience. For more detailed insights, refer to the features of Virtual DOM in React.

Here are some important features:

• Efficient Updates
  React updates only the parts of the DOM that have changed, which makes the update process faster and more efficient.
• Reconciliation Process
  React uses a diffing algorithm to compare the current and previous Virtual DOMs, ensuring minimal updates to the actual DOM.
• Improved Performance
  By minimizing direct manipulations of the real DOM, the Virtual DOM reduces unnecessary rendering, leading to better performance, especially in complex applications.
• Cross-Platform Consistency
  Virtual DOM ensures that components are rendered consistently across different platforms, making React applications more reliable across various devices and browsers.

Key Concepts of Virtual DOM

• Representation: The Virtual DOM is an in-memory representation of the actual DOM.
• Efficiency: It enables efficient updates by comparing changes between the virtual and real DOMs.
• Minimization: Only the necessary changes are applied to the real DOM, minimizing performance overhead.
• Diffing Algorithm: React's reconciliation process identifies differences between virtual DOM trees and optimally updates the actual DOM.
• Performance: By reducing the number of expensive DOM operations, React's Virtual DOM enhances rendering speed and application responsiveness.
• Abstraction: Developers interact with the Virtual DOM through React's APIs, abstracting away direct manipulation of the underlying DOM for cleaner code.

How is Virtual DOM different from Shadow DOM?

A shadow DOM helps in providing isolation and encapsulation of CSS and DOM in web components. It helps in creating self-contained containers which have their own styling and DOM tree. Shadow DOM ensures that these styling and DOM tree are not affected by external styles or scripts. In simple words, shadow DOM’s help in isolating components and even their styles from the actual DOM. It also ensures that their appearance or behavior is not affected by other elements' styles.

The shadow DOM can be enabled in Chrome DevTools from the “Settings” Option. We can enable the "Show user agent shadow DOM" option present under the “Elements” section to view the Shadow DOM.

 
A virtual DOM in comparison to shadow DOM helps in making the updation of UI faster by updating only the changed objects in the actual DOM while a shadow DOM helps in providing isolation and encapsulation of CSS and DOM in web components.

Difference Between DOM and Virtual DOM in React

Advantages of Virtual DOM

1. Improved Performance: The Virtual DOM minimizes direct interaction with the real DOM, resulting in faster rendering and better performance by updating only the parts that have changed.
2. Efficient Re-rendering: React uses the diffing algorithm to identify minimal changes between the Virtual DOM and real DOM, preventing unnecessary re-renders and ensuring a smoother user experience.
3. Faster Updates: With Virtual DOM, React batches updates and applies them in a single pass, reducing the time spent in re-rendering and improving the responsiveness of the application.
4. Enhanced User Experience: React ensures that only the necessary components are updated, leading to a more responsive interface with fewer delays and less flickering.
5. Cross-Platform Consistency: The Virtual DOM abstracts the differences between platforms, ensuring that components render consistently across different devices and browsers.

Disadvantages of Virtual DOM

1. Memory Overhead: Maintaining a separate virtual DOM consumes memory, potentially increasing the overall memory footprint of the application.
2. Initial Render Overhead: The initial rendering process in React can be slower due to the overhead of creating and reconciling the virtual DOM.
3. Learning Curve: Understanding the concept of a virtual DOM and how it operates requires developers to grasp additional complexity compared to traditional DOM manipulation.
4. Potential Performance Bottlenecks: In certain scenarios, the diffing and reconciliation process of the virtual DOM can become a performance bottleneck, especially in applications with complex UI structures or frequent updates.
5. Indirect DOM Manipulation: Working with the virtual DOM adds an extra layer of abstraction, which may make it challenging to debug and troubleshoot issues related to direct DOM manipulation.

Frequently Asked Questions

What is React DOM used for?

React DOM is used to render React components into the actual DOM and manage updates efficiently, ensuring smooth interaction between React and the web page.

Why is virtual DOM faster?

The Virtual DOM is faster because it minimizes direct manipulation of the real DOM, updating only the changed parts after a diffing process.

Which algorithm is used in virtual DOM?

The "diffing algorithm" is used in the Virtual DOM to compare the previous and updated versions, determining minimal changes to apply to the actual DOM.

Why do we use virtual DOM in React?

Virtual DOM in React is used as a strategy to compute minimal DOM operations while re-rendering the UI. It is not in competition with or faster than the real DOM. The virtual DOM gives a mechanism that abstracts manual DOM manipulations away from the coders, which helps in writing more predictable code.

Who creates virtual DOM in React?

The Virtual DOM is created by React itself. React automatically generates a lightweight copy of the real DOM whenever a component's state or props change, ensuring efficient rendering and updates.

What is the role of the virtual DOM?

Virtual DOM in React is used to enhance its performance. It uses the observable to determine state and prop changes. React uses an efficient diff algorithm for comparing the versions of virtual DOM.

Conclusion

In this article, we have discussed Virtual DOM in React. The Virtual DOM in React stands as a powerful optimization tool, offering significant benefits in terms of performance, efficiency, and developer experience. By abstracting away direct manipulation of the underlying DOM, React's Virtual DOM enables efficient rendering, minimizing unnecessary updates and enhancing application responsiveness.

Recommended Readings:

• Advantages and Disadvantages of React JS
• React.js Framework
• Use of render() in React js
• Rendering Elements in ReactJs
• React Reconciliation