React DOM/Virtual DOM

12 min read

There are hundreds of articles floating which deal with the comparison of DOM and React-DOM.But what is React-DOM or what is DOM for that matter.Let’s unwind this.

Advantages of React

React, often stylized as React-dom, has taken the world of web development by storm. Recognizing the advantages of React and how it interacts with the Document Object Model (DOM) – a topic that often prompts the question, “what is DOM in React?” – is essential for both aspiring and seasoned developers. From the component-based approach and React DOM methods to the virtual DOM concept, React brings several benefits to the table.

Optimized Performance with Virtual DOM

One of the foremost advantages of React is the implementation of the virtual DOM. React DOM’s ability to minimize direct manipulation of the actual DOM – an operation that’s computationally expensive and can slow down your app – sets it apart from many other JavaScript libraries and frameworks.

React’s virtual DOM works by creating a replica of the actual DOM, allowing React to calculate the most efficient way to make changes. This involves using React DOM methods for ‘diffing’ (comparing the old and new DOM), and ‘reconciliation’ (updating the actual DOM to match the new virtual DOM). The overall result? Faster, more efficient applications that provide a smoother user experience.

Component-Based Architecture

Another crucial advantage of React is its component-based architecture. This approach allows developers to build applications using reusable components, fostering code maintainability and reusability. Each component in React has its own state and logic, which makes it self-contained and helps in isolating bugs and making testing easier.

Even while managing these components, React avoids direct DOM manipulation. In case you need to access the DOM directly, React provides escape hatches such as the Reactdom.finddomnode method, although it’s generally discouraged.

Seamless Integration and Backward Compatibility

React’s design allows it to be gradually adopted, meaning you can implement it in small parts of your project without needing to overhaul the entire codebase. This makes React a flexible solution that can be introduced into existing projects, making the transition smoother and less disruptive.

Also, React strives to be backward-compatible. This means that updates to the library aim not to break your existing code. You can keep your React projects updated with the latest features and improvements without worrying about significant refactorings.

Server-Side Rendering with Reactdom.hydrate

React also supports server-side rendering (SSR), which can improve the initial load performance of your application and make it more SEO-friendly. SSR works by rendering React components on the server and sending the HTML to the browser. The Reactdom.hydrate function is used to make the server-rendered markup interactive, ensuring a seamless user experience.

Rich Ecosystem and Community Support

The popularity of React has led to a rich ecosystem of libraries, tools, and resources. From state management libraries like Redux and MobX, to routing solutions like React-router, there’s a package for almost every need. Moreover, you’re joining a vibrant community of developers when you start working with React. This means a wealth of tutorials, guides, and third-party tools are at your disposal.

Important Points to Remember While Working with React

React, a powerful JavaScript library created by Facebook, has become a vital tool for building interactive web applications. As you embark on your React development journey, there are several key points to remember. Notably, understanding React DOM, Reactdom.finddomnode, and Reactdom.hydrate, along with other important React DOM methods, is critical to your success.

Component-Based Approach

At the heart of any React application lies a component-based approach. This means that a React app is built using numerous individual pieces, or components, each responsible for a distinct part of the user interface. This modular approach has several advantages:

  • It promotes code reuse, as components can be used in multiple places throughout an application.
  • It makes code more manageable and easy to test, as each component has its own logic and controls its own rendering.
  • It simplifies the debugging process, as developers can isolate issues to specific components.

While working with components, you’ll often encounter React DOM manipulation. It’s important to note that the direct manipulation of the DOM is generally avoided in React. Instead, the state of components is updated, leading to a change in the virtual DOM, and eventually, an efficient update of the actual DOM.

Furthermore, React provides several methods to help manipulate the DOM when necessary. Reactdom.finddomnode is one such method, allowing you to directly access a DOM node. However, it’s considered an escape hatch and its use is discouraged in most cases.

Declarative Views in React

Another essential point to remember while working with React is its declarative nature. When you write a React component, you don’t tell the program how to update the view when your data changes. Instead, you describe what the view should look like.

React, with the help of its virtual DOM, efficiently updates and renders the appropriate components when your data changes. The process involves diffing (comparing the new virtual DOM with the previous one) and reconciliation (updating the real DOM to match the virtual DOM).


Reactdom.hydrate comes into play when you’re dealing with server-rendered applications. It enables the client-side React to recognize and preserve the server-rendered markup, making the app interactive.


What is DOM in React?


DOM is short form of Document Object Model and is actually is just a  Javascript object which is logical representation of any web page.This Javascript object or DOM is structured in the form of tree and this tree contains all the elements and its properties.And this elements are treated as nodes.

Whenever during development there is any change in any of the elements the DOM is required to be updated which implies that the browser has to calculate and load all the nodes.And then load all the css file, technically speaking repaint the whole web page as per the CSS. This makes the reload of the web page very slow and so we say the DOM-manipulation used to be costly before react-dom.

How Virtual DOM Works in React?

React’s power and efficiency come from its unique approach to handling updates in a web application. A cornerstone of this approach is the usage of a virtual DOM. Let’s break down how the virtual DOM works:

  • Initial Render

When a React application is first loaded, React DOM creates a lightweight copy of the actual DOM, a process known as the creation of a “virtual DOM”. This is not the visible webpage but a representation of it in memory.

  • Component Updates

As users interact with the application or data changes, your components may update. These updates could be state changes or prop updates. When an update occurs, React creates a new virtual DOM to reflect these changes.

  • Diffing

React then compares this new virtual DOM (with the updates) to the previous virtual DOM. This process is known as “diffing”. React identifies which objects have changed in the virtual DOM through this process.

  • Reconciliation

The final step is “reconciliation”. Here, React uses the results from the diffing process to efficiently update the actual DOM. It only updates the parts of the real DOM that have changed in the virtual DOM, not the entire page. This leads to significant performance improvements, as manipulating the real DOM is a costly operation.

  • Reactdom.finddomnode

It’s worth noting that Reactdom.finddomnode is a method in React DOM that allows direct access to a DOM node. It’s often used when you need to interact with the actual DOM, rather than the virtual one.

  • Reactdom.hydrate

Another important method is Reactdom.hydrate, which is used to “hydrate” a container whose HTML contents were rendered by ReactDOMServer. Hydrating, in this context, means attaching event listeners to the server-rendered markup functional, interactive application.

  • Optimization

This entire process of dealing with the virtual DOM makes React highly optimized. Since the real DOM manipulations, which are expensive operations, are minimized, the application becomes highly efficient and much faster.

  • Batched Updates

Another benefit of this process is that React batches multiple updates together to avoid unnecessary re-renders. This further boosts the application’s performance.

So how does react-dom solve this problem??? 

 React-DOM provides a specific bundle of packages to DOM that can be applied only to the top level of the app instead of all the components. React DOM comes with some methods.

We will discuss these methods later but it is important to mention here that react-dom or virtual dom is nothing but a copy of the original javascript dom object.

So whenever there is any manipulation in any of the element the virtual DOM updates itself(here updating the virtual dom comparatively much cheaper) and only the differences between the virtual dom and real dom gets updated in real dom(For example if the element already rendered in the real dom then only changes after comparison between real dom and virtual dom will be re-rendered and the whole element).

So here there is no direct manipulation in the real dom and which implies faster load of web page.

Now let’s have a deep dive into react-dom  and the methods provided by it such as

render()  : This method renders the react element to the given container in the dom and returns a reference of container or else null if its a stateless container and if there are any callbacks functions passed to it then executes them only once the component is rendered.The syntax for the same is as follows

ReactDOM.render(element, container[, callback])

hydrate() : Hydrate works same as render method and follows the same syntax as follows

ReactDOM.hydrate(element, container[, callback])

But it is used to hydrate the container whose html markups are rendered by the reactDomServer.When I say hydrate the container by that what I mean is react try to compare the content rendered at the client is whether the same as the server or not. React generally ignore the mismatches in the text content but it doesn’t work the same way in case of mismatches with the attributes.

If you have some content which is rendered differently at server and client then you can suppress the warning by using suppressHydrationWarning .But always guided to keep in mind to avoid using this as it might lead to some unexpected bug.

unmountComponentAtNode() : As the name of this method is self explanatory.It unmounts the component and it cleans its event handler from the DOM. The syntax for the same is as follows


Also this method returns false if there is no component to unmount and returns true it has successfully unmounts the component.


findDOMNode() : This method is an escape hatch as it will let you access the underlying DOM node.But ideally it is preferable as it pierces the component abstraction.You can not use this method in strict mode as it has been deprecated.The syntax to use the same is as follows :



If this component is mounted into the DOM , it  returns native browser DOM element and it the component is rendered to null or false then findDOMNode(component) returns null else in case of findDOMNode is rendered to string then the component will return text dom containing thar value.


Also findDOMNode only works in case of the component that has been already rendered.If you try to use this on the component that does not exist on dom or still has to be rendered (for example the components in render method) then findDOMNOde will throw an exception.

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