Virtual Dom|Browser DOM what are these in React Js?

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What is DOM?

The Document Object Model (DOM) plays a crucial role in interactive web development. But what is DOM in React JS, and why is it so essential? When you’re working with React, the DOM in React is your interactive connection between the JavaScript code and the rendered website content. React utilizes the Virtual DOM to improve the efficiency of this connection.

Fundamentally, the DOM is a platform- and language-neutral interface that allows scripts and programs to dynamically access and update the content, structure, and style of a document. It represents the structure of HTML documents, like a tree, where each branch ends in a node, and each node contains objects. This structure is essential when you’re working with JavaScript and frameworks like React, where the DOM React connection is key to functionality.

The concept of the Virtual DOM in React JS comes into play as a lightweight copy of the actual DOM. This ‘virtual’ version provides several advantages, as React Virtual DOM enhances the efficiency of rendering changes to the user interface, making React a standout choice for developers focusing on user experience.

What is DOM in React?

Document Object Model  (DOM) is Javascript Client-Side API to represent and manipulate Document (HTML/XML).



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How does Javascript generate a Document Object model out of it?  Every tag is a node. so HTML, head, body, title, a, pare nodes, Except link and script tags are not considered as a node. HTML will be the parent node and everything else will be children of the HTML.

So, the tree is generated as,

This is not how the Data Structure is stored in Javascript. Html is not a root node. JavaScript has its prototype chain so Html is one node that is inherited from Object. Prototype so that it gets the methods to calculate styles, properties, Manipulating the individual nodes.

Please go through the below picture you will get a better idea.

Now, If you can see the highlighted part is from where our HTML node starts forming a tree. And we consider it as a DOM object. If you can see CSS style declaration is a sibling of node/Html and that is why it is not present in the subtree of HTML as a parent.

As we know HTML/node is inherited from Object. Prototype and Dom will get many methods to retrieve and manipulate the document object model. This is the reason we say JavaScript is an untyped language that is used to make HTML dynamic.

What makes DOM manipulation slow?

Understanding what makes DOM manipulation slow is vital in identifying why solutions like the Virtual DOM React uses are beneficial. Traditional DOM manipulation is known to be resource-intensive. The problem stems from the fact that every small modification in the DOM can cause the browser to recalculate CSS styles, layout, and render the page. These recalculations can result in a significant performance hit, especially when complex interactions or large data manipulations are taking place.

However, this is where the concept of the Virtual DOM in React steps in. React’s Virtual DOM allows for a more efficient update process. Instead of making direct changes to the browser DOM, changes are initially made to the Virtual DOM in React. React then uses efficient diffing algorithms to determine the minimum number of changes necessary to update the actual DOM. By batching multiple changes together, React avoids the costly overhead of multiple direct manipulations of the Browser DOM.

This approach, adopted by the Virtual DOM React JS uses, helps optimize performance and leads to smoother, faster updates in the user interface. So when it comes to understanding what is DOM in React JS, it’s equally important to appreciate the ingenious solution that the React Virtual DOM provides to slow DOM manipulation.

These two aspects together – the role of the DOM and the benefit of the Virtual DOM – are what makes React JS such a powerful tool for web development.

If Document Object Model is so cool, then why go with Virtual DOM?

Although you have all the methods to change the DOM tree it comes with a lot of costs. If you want to change some child nodes. Javascript has to repaint the window with margin, padding, color, etc. properties. Document object model knows how to re-render the page but it is not so intelligent to keep track of each node and change only the node which is changing.


Let’s take an example,

You have asked to decorate the room with 100 balloons. You have decorated the room with 100 balloons.

Now your mentor told you the color of each balloon should be red. so you remove all the balloons and now decorate the room with red balloons.

The mentor comes and asks you now change balloon no 90 with a blue-colored balloon. now you remove all balloons and bring 99 red balloons and 1 blue balloon and paint accordingly.

The mentor comes and asks please change balloon no 80 to green. You remove all the balloons. Go market bring 98 red, 1 blue, 1 green. And decorate the room accordingly.

WOW, will you work this way? No. right? but your Document Object Model does. So, how to make DOM intelligent?

Now, VIRTUAL DOM comes to rescue us.


What is the Virtual DOM in React JS?

It is a React’s Object that represents the Browsers DOM, Which is intelligent to make changes in the DOM with the help of the Diff Algorithm. Few Blog says, it is so fast that it can produce 20000 nodes per second.

For every DOM object, there is a React Virtual DOM object. In simpler terms, virtual DOM in React JS is like a lightweight copy of a DOM object. 

Are you wondering how is virtual dom in react js different from real DOM? React Virtual DOM has properties the same as real DOM object. However, it lacks the power to change the screen immediately. 

Further, DOM manipulation is slower. Virtual DOM in React JS supports faster manipulation. This is because it doesn’t let anything be drawn on the screen. In layman’s terms, instead of moving actual rooms in a house, you edit the blueprint.


Now, How does Virtual DOM work?

  1. Whenever a Document Object Model is rendered into a browser React generates a copy of that object as a Virtual DOM.
  2. When the user interacts and we want to change the Document Object Model, first we generate another copy of it.
  3. We compare virtual DOM vs another copy of it, if there are changes then only we will render the Browser Document Object Model, otherwise, we won’t.
  4. Now if we got some changes between them, react is intelligent to find which node has changed. React tells browser Document Object Model “Hey! this node subtree needs to change, everything else remains as it is”.
  5. Browser thanks to react saying, I am very good at painting things but you told me where to paints and that’s why we are doing fast.

Pros and Cons of Virtual DOM

In the web development world, the concept of the Virtual DOM in React JS has sparked a significant conversation about efficiency and performance. Before diving into the pros and cons, let’s first address the question – what is Virtual DOM in React JS?

Virtual DOM in React JS is a lightweight copy or ‘virtual’ representation of the actual DOM. This concept introduces a high-performance algorithm for syncing updates between the Virtual DOM and the Real DOM, making React Virtual DOM vs Real DOM a fascinating comparison.

Understanding the Virtual DOM begins with asking, “Where is Virtual DOM stored in React?” React creates this Virtual DOM in its memory. Every time a component’s state changes, a new Virtual DOM tree is created. This new tree is then compared with the previous tree, a process known as diffing. React then smartly updates the Real DOM, applying only the differences identified during the diffing process.

Now let’s delve into the advantages and drawbacks of this approach.


  • Performance Optimization: React’s use of a Virtual DOM helps to minimize direct manipulations of the Real DOM, resulting in significant performance improvements. It does this by batch updating, only applying differences to the Real DOM rather than redrawing the entire DOM tree with each change.
  • Less Redundant Code: With Virtual DOM, developers can write declarative code. Instead of worrying about how to change the view to reflect the state, they merely declare what the view should look like.
  • Improved User Experience: By speeding up the update process, the Virtual DOM in React JS can provide a smoother, more responsive user experience.


  • Overhead Cost: While the Virtual DOM improves performance for large apps, it does introduce an overhead cost. For simple applications, this might be more than the cost of just updating the Real DOM directly.
  • Memory Usage: A copy of the Real DOM is stored in memory, which could lead to higher memory usage.
  • Compatibility Issues: React’s Virtual DOM might not be fully compatible with other libraries that also manipulate the DOM.

Understanding what is React Virtual DOM and how the Virtual DOM works in React is essential in today’s fast-paced web development environment. Despite some drawbacks, the Virtual DOM provides an effective solution for rendering large-scale, high-performance applications. To put it simply, the DOM full form in React JS – the Document Object Model – is a critical piece of web development, but with the Virtual DOM, React JS offers a modern, efficient, and powerful twist on this standard model.

How is the Virtual DOM Different from the Real DOM?

When we talk about React, the conversation inevitably turns to the Virtual DOM in ReactJS and how it differentiates from the Real DOM. If you’re wondering what is Real DOM in React JS, let’s begin with a brief introduction.

The Real DOM (Document Object Model) in ReactJS is the standard model for interacting with the structure of your web page. It is a tree-like representation of your HTML content that JavaScript can interact with, making dynamic changes to the visible layout and content. But the interaction with the Real DOM can be slow and inefficient, especially when there are frequent changes. That’s where the Virtual DOM in ReactJS comes into play.

React introduces a Virtual DOM to optimize interactions and updates to the webpage. Instead of making direct changes to the Real DOM (which can be computationally expensive), React first makes changes to the Virtual DOM. But how many Virtual DOM in React exist? In reality, there are two Virtual DOM trees involved in this process at any given point: the current Virtual DOM and the updated Virtual DOM reflecting the new state after changes.

Difference between Virtual DOM in ReactJS and the Real DOM

  • Efficiency: The most crucial difference lies in the efficiency of updates. Direct changes to the Real DOM can be slow, particularly if they trigger page re-renders. React instead applies changes to the Virtual DOM and then uses a diffing algorithm to apply only necessary updates to the Real DOM, increasing performance.
  • Batch Updates: Another key difference is how updates are handled. The Real DOM updates immediately whenever a change is made, which can be costly in terms of performance. On the other hand, React batches multiple changes together on the Virtual DOM before applying them to the Real DOM, resulting in fewer actual DOM manipulations.
  • Memory Efficiency: The Real DOM resides in the browser’s memory and gets directly affected by changes, whereas the Virtual DOM is a lighter-weight copy that resides in the application’s memory, making changes less resource-intensive.

To fully understand what is the DOM in React, it’s essential to comprehend both these aspects – the Real and the Virtual DOM. The addition of the Virtual DOM to ReactJS is a revolutionary approach to improving web app performance. 

How is the Virtual DOM Different from the Shadow DOM?

Understanding the difference between the Virtual DOM and the Shadow DOM is an essential aspect of mastering modern web development. Each serves a unique purpose and provides different benefits. But before we delve into their differences, let’s review how the Virtual DOM works in React JS and React Native and how it compares to the Real DOM in React JS.

In React JS, the Virtual DOM is a lightweight representation of the Real DOM. This virtual representation improves performance by reducing the amount of direct manipulation on the resource-intensive Real DOM. Instead of directly modifying the Real DOM (which can trigger costly page re-renders), the Virtual DOM batches multiple changes together and applies them all at once. This difference between the Virtual DOM and Real DOM in React JS is a key factor in why we use Virtual DOM in React.

Now, let’s consider the Shadow DOM. The Shadow DOM is a web standard that enables encapsulation in the browser. It allows for the creation of a separate, isolated DOM tree attached to an element of the Real DOM, without affecting other parts of the DOM tree.

Difference between the Virtual DOM and the Shadow DOM

  • Scope: While the Virtual DOM represents the entire HTML document and is used for diffing and efficiently updating the Real DOM, the Shadow DOM is used to create an isolated DOM tree for a specific element, ensuring styles and scripts are scoped to that tree and do not leak out.
  • Implementation: The Virtual DOM is an application-level implementation used primarily in libraries like React JS and React Native, whereas the Shadow DOM is a browser technology built into the web platform.
  • Purpose: The Virtual DOM’s main purpose is to provide a performant way to update the view, given the use of Virtual DOM in React JS. On the other hand, the Shadow DOM provides style encapsulation and avoids style conflicts in the larger DOM tree.

Understanding how the Virtual DOM works in React Native and React JS, compared to the Shadow DOM, underscores the versatility and diversity of tools available for managing and interacting with the DOM in modern web development. Both serve unique purposes, and their use depends largely on the specific needs and goals of your project.

Comparison Chart: Real DOM vs. Virtual DOM vs. Shadow DOM

When it comes to managing and interacting with web content, understanding the differences between the Real DOM, Virtual DOM, and Shadow DOM is crucial.


 understanding the differences between the Real DOM, Virtual DOM, and Shadow DOM allows developers to better manage web content and optimize application performance. Each has its unique benefits and potential drawbacks, and their usage depends largely on the specific requirements of the project.

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