Hello there!

Ever wondered what lies behind the scenes of web applications that offer seamless, almost magical user experiences?

The key to their remarkable performance often revolves around an intriguing concept known as the Virtual DOM. In this blog, we embark on an exciting journey to demystify the Virtual DOM, shed light on its pivotal role in elevating React’s capabilities, and explore how it can redefine your approach to web development.

The idea behind the Virtual DOM (VDOM) is that a library called React DOM maintains an ideal or “virtual” representation of a user interface in memory and synchronizes it with the “real” DOM.

What is DOM and VDOM?

The Document Object Model (DOM) serves as a programming interface for both HTML and XML documents. It essentially presents the document’s structure in the form of a tree made up of nodes. This interface allows scripts to interact with and make changes to the content and structure of the document, providing a means for dynamic manipulation and control of web page elements.

Representation of DOM

The interface that connects JavaScript code to a webpage’s structure is called the Document Object Model (DOM). The DOM needs to be updated each time a page’s structure changes, which can be slow, particularly in complex applications with many elements.

In React, the DOM is the representation of an HTML or XML document in memory, and the React DOM is a package that allows React components to render and update the actual DOM. When a React component’s state or properties change, the React DOM updates the actual DOM to reflect those changes.

React Virtual DOM (VDOM) is an abstract representation of a real DOM. In other words, the VDOM acts as an intermediary between the React components and the actual DOM, providing a high-performance way to update the user interface.

The React Virtual DOM is a concept that plays a crucial role in the library’s performance and efficiency. Modifying the DOM directly can be slow for complex applications. This limitation has led to the development of the virtual DOM (VDOM) concept.

When a component’s state or properties change, React updates the VDOM, which then calculates the minimum number of actual DOM updates required to reflect the changes. This process of updating the VDOM first before updating the actual DOM results in much faster updates, as the cost of changing the real DOM is significantly higher compared to updating the virtual DOM.

Exploring VDOM

As we spoke already, making changes directly in the DOM is something that shouldn’t be done more often because it is a slow process.

React Virtual DOM solves this problem by providing an in-memory representation of the actual DOM, allowing for fast and efficient updates. When a component’s state or properties change, React first updates the Virtual DOM, then calculates the minimum number of actual DOM updates necessary to reflect those changes.

This process is significantly faster than directly updating the real DOM, primarily due to the considerably higher cost associated with making changes to the actual DOM.

Here’s how it works in more detail:

1. React updates the Virtual DOM: When a component’s state or properties change, React updates the Virtual DOM to reflect the changes.

2. Virtual DOM diffing: React then compares the updated VDOM with a previous version of the VDOM to determine the minimum number of updates necessary to the actual DOM. This process is called “diffing.”

3. Batch updates to the actual DOM: React then batches the necessary updates to the actual DOM, reducing the number of DOM updates and minimizing the impact on performance.

Reconciliation

Reconciliation is the process by which React updates the VDOM to reflect changes in the underlying data. This is a fundamental idea in React and is employed to update the user interface efficiently when a component’s state changes.

When a component’s state or props change, React re-renders the component and creates a new VDOM representation. Then, it compares the new virtual DOM with the previous virtual DOM to determine the minimum number of changes necessary to update the actual DOM. This process is known as reconciliation.

React uses a fast and efficient algorithm to compare the VDOM trees and determine which parts of the actual DOM need to be updated. If a component’s state or props haven’t changed, React can simply reuse the previous VDOM tree, rather than creating a new one from scratch. This results in faster updates and better performance.

React also provides a set of life cycle methods that allow developers to control the reconciliation process, such as shouldComponentUpdate and forceUpdate, which can be used to optimize the performance of components.

Diffing

Diffing is the process of determining the differences between two VDOM trees in React.

During reconciliation, it plays a role in figuring out which sections of the actual DOM require updates when there are changes in a component’s state or props.

React uses diffing to compare the previous VDOM tree with the new VDOM tree that is generated when a component is re- rendered. The diffing algorithm compares the two trees and identifies the minimum number of changes necessary to update the actual DOM to match the new VDOM.

The diffing algorithm works by recursively comparing the nodes in the two VDOM trees, starting from the root node. If a node in the previous VDOM tree is of the same type as a node In the new VDOM tree and has the same props.

The diffing algorithm works by recursively comparing the nodes in the two virtual DOM trees, starting from the root node. When a node in the previous VDOM tree matches a node in the new VDOM tree in both type and props, it’s considered unchanged, and its children are then compared recursively.

If a node in the new VDOM tree is different from the corresponding node in the previous VDOM tree, it is assumed that the node has changed and the corresponding part of the actual DOM is updated.

React also provides a way to optimize the diffing process by using keys on elements. When an element is given a key, React uses the key to match elements between the previous and new VDOM trees, rather than comparing the entire tree.  This enables React to swiftly identify elements that have changed and those that haven’t, leading to faster and more efficient updates.

Example

Consider a simple component that displays a list of items:

When the component is rendered, React generates a virtual DOM representation of the component, as follows:

When the component’s props are updated, React will re-render the component and create a new VDOM representation. For example, if the list of items changes,

From [{id: 1, text: “Item 1”}, {id: 2, text: “Item 2”}, {id: 3, text: “Item 3”}]

To [{id: 2, text: “Item 2”}, {id: 4, text: “Item 4”}, {id: 5, text: “Item 5”}]

The new virtual DOM will look like this:

React will then calculate the difference between the old VDOM and the new VDOM and update only the necessary elements in the actual DOM. This approach significantly accelerates and enhances the efficiency of updates compared to updating the entire DOM tree.

Top 7 Features of React Virtual DOM

The React Virtual DOM offers several key features that make it an efficient and powerful tool for building user interfaces:

1. Faster updates: By using a virtual representation of the DOM, React can calculate the minimum number of changes necessary to update the actual DOM, which is much faster than updating the entire DOM tree.

2. Better performance: React’s diffing algorithm is optimized for speed, and by only updating the necessary parts of the DOM, React can improve the overall performance of your application.

3. Easy-to-use API: React provides a simple and intuitive API for building and updating the VDOM, making it easier to build and maintain complex user interfaces.

4. Improved modularity: The VDOM provides a way to separate the render logic from the actual DOM, which makes it easier to manage and reuse components.

5. Server-side rendering: React virtual DOM makes it possible to perform server-side rendering, which can improve the initial loading performance of your application and make it more accessible to search engines.

6. Better testing: React Virtual DOM provides a way to write fast and reliable tests for your user interface components, making it easier to ensure that your components behave as expected.

7. Reactive updates: The VDOM provides a way to automatically re-render components when the underlying data changes, making it easier to build dynamic and reactive user interfaces.

In Closing

The Virtual DOM (VDOM) stands as a cornerstone of React’s remarkable speed and efficiency. It’s the key to unlocking swifter, more responsive user interfaces and enhancing the overall performance of React applications.

If you’re intrigued by the potential of the Virtual DOM or have questions, don’t hesitate to reach out to us at KaarTech. We’re here to guide you through the enthralling world of React and beyond. Your journey to supercharged web development starts here.

 

FAQ’s

What is the React Virtual DOM?

The Virtual DOM (VDOM) is an abstract representation of the real DOM. It acts as an intermediary between React components and the actual DOM, allowing for faster and more efficient updates.

How does the Virtual DOM improve performance?

React updates the Virtual DOM when a component’s state or properties change. It then calculates the minimum number of changes needed to update the actual DOM. This process is significantly faster than updating the real DOM directly.

What is reconciliation’s role in React?

Reconciliation is the process of efficiently updating the UI when a component’s state or props change. React compares the new and previous virtual DOM representations to determine the minimal changes required to update the actual DOM.

What are the key benefits of React Virtual DOM?

Key benefits include faster updates, better performance, an easy-to-use API, improved modularity, support for server-side rendering, enhanced testing capabilities, and the ability to build dynamic and reactive user interfaces.