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What is Virtual DOM in React?

What is Virtual DOM in React?

The Document Object Model, commonly referred to as the DOM, is a critical concept in web development. Understanding it is vital for React developers. In React, the DOM represents the structure of a web page and provides a programming interface for manipulating it. 

It serves as an intermediary between your React components and the actual web page, enabling you to create interactive and dynamic user interfaces. By learning the react DOM’s significance within React, you’ll gain the ability to build powerful applications with seamless user experiences. 

Table of Contents

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What is DOM in React?

What is DOM in React

The Document Object Model (DOM) in React is an abstraction of the web page’s structure and content. It represents the HTML elements as a tree-like structure that can be accessed and manipulated through JavaScript. React utilizes the DOM to render and update components efficiently. 

When a React component is rendered, it generates a virtual representation of the DOM, known as the Virtual DOM. React then compares the changes in the Virtual DOM with the actual DOM and applies the necessary updates only where required, optimizing performance. 

How Does React Use Dom

React uses the DOM (Document Object Model) to render its UI and to create and update its UI components.

React efficiently utilizes the DOM by selectively updating only the elements that have undergone changes. This smart approach prevents any unnecessary DOM operations, resulting in improved web application performance.

Here is an example of how React uses the DOM:

function App() {
  return (
    <div>
      <h1>Hello World</h1>
      <p>This is a paragraph.</p>
    </div>
  );
}

Upon rendering this component, React generates a Virtual DOM (VDOM) that mirrors the component’s HTML representation. Subsequently, React compares this VDOM with the real DOM, and any differences identified are then applied to the actual DOM.

For exmaple, when the content of the h1 element is modified, React will specifically update the corresponding DOM element that represents the h1 element. As a result, this targeted update prevents any redundant DOM operations, like the creation and removal of DOM elements.

React’s adoption of the DOM is among the key factors contributing to its widespread popularity as a library for web application development. Its efficiency, user-friendly nature, and high degree of adaptability make it a favored choice for developers.

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What is Virtual DOM in React?

What is Virtual DOM in React

The Virtual DOM in React is a lightweight, in-memory representation of the actual Document Object Model (DOM). When you create a React component, React generates a virtual copy of the DOM hierarchy associated with that component. 

This Virtual DOM is a JavaScript object that holds the component’s structure, properties, and state. When updates occur in the component, React efficiently calculates the differences between the previous and new Virtual DOM representations. It then selectively applies these changes to the real DOM, minimizing costly direct manipulations.

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How Does the Virtual DOM Work in React?

The Virtual DOM is a crucial concept in React that significantly contributes to its efficiency and performance. Here’s a detailed explanation of how the Virtual DOM works in React:

  • Initial Rendering: When a React component is first rendered, it creates a corresponding Virtual DOM representation. This Virtual DOM is a tree-like structure that mirrors the actual DOM elements.
  • Virtual DOM Diffing: When a state or prop of a React component changes, a new Virtual DOM representation is created. React then performs a process called “diffing” by comparing the previous Virtual DOM with the new one.
    • Element reconciliation: React performs a diffing algorithm that efficiently reconciles the differences between the previous and new Virtual DOM trees. It identifies the minimal number of operations required to update the actual DOM.
  • Update Computation: During the diffing process, React determines which components need to be updated. It compares the previous and new Virtual DOM elements and identifies any differences.
    • Efficient Updates: React optimizes the updates by minimizing the number of changes that need to be made to the actual DOM. Instead of updating every element individually, it batches the changes and performs them in a single update for better performance.
  • Virtual DOM Patching: After determining the updates needed, React applies those changes to the actual DOM. This process is known as “patching.” It only modifies the specific elements that require updates rather than re-rendering the entire user interface.
    • Efficient Rendering: React updates the actual DOM only where necessary, which reduces the overall rendering time and improves the application’s performance.

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How to Install React Router Dom?

To install React Router Dom, you can follow these steps:

Step 1: Set Up a React Project
Before installing React Router Dom, you need to have a React project set up. You can create a new React project using Create React App or any other method you prefer. Make sure you have Node.js and npm (Node Package Manager) installed on your system.

Step 2: Open the Command-Line Interface
Open your command-line interface, such as Terminal (for macOS and Linux) or Command Prompt (for Windows).

Step 3: Navigate to the Project Directory
Navigate to the directory where your React project is located. You can use the ‘cd’ command followed by the path to your project directory.

For example:
cd path/to/your/react-project

Step 4: Install React Router Dom
To install React Router Dom, run the following command in your command-line interface:

npm install react-router-dom

This command will use npm to download and install the React Router Dom package from the npm registry.

Step 5: Wait for the Installation
Wait for the installation process to complete. npm will download the package and its dependencies and set them up within your project.

Step 6: Start Using React Router Dom
Once the installation is finished, you can start using React Router Dom in your React project. Import the required components from the ‘react-router-dom’ package and use them in your code.

For example, in your JavaScript file,

import { BrowserRouter, Route, Switch } from 'react-router-dom';
// Your React component code
<BrowserRouter>
  <Switch>
    <Route exact path="/" component={Home} />
    <Route path="/about" component={About} />
    <Route path="/contact" component={Contact} />
  </Switch>
</BrowserRouter>

In this example, we imported ‘BrowserRouter’, ‘Route’, and ‘Switch’ from ‘react-router-dom’ and used them to set up routing for the specified paths.

That’s it! You have successfully installed React Router Dom and can now utilize its routing capabilities in your React project.

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Real DOM Example

Let’s consider a simple example to understand how the Real DOM works. Suppose we have the following HTML code:

<!DOCTYPE HTML>
<html>
  <head>
    <title>My Web Page</title>
  </head>
  <body>
    <h1>Welcome to My Web Page!</h1>
    <p>This is a paragraph.</p>
  </body>
</html>

When the browser encounters this HTML code, it creates a corresponding Real DOM structure. It would look something like the following:

Real DOM Example

In the Real DOM, each element, such as ‘<html>’, ‘<head>’, ‘<body>’, ‘<h1>’, and ‘<p>’, is represented by a node. The text content, like “My Web Page,” “Welcome to My Web Page!,” and “This is a paragraph.,” is stored as the text value of the corresponding nodes.

The Real DOM is important because it allows JavaScript to manipulate the structure and content of a web page dynamically. For example, you can use JavaScript to add new elements, modify existing ones, or remove elements from the Real DOM. These changes will be reflected visually on the web page.

Virtual DOM Example

Let’s illustrate the concept of Virtual DOM with an example. 

Consider a React component that renders a simple to-do list:

import React from 'react';
function TodoList() {
  return (
    <div>
      <h1>Todo List</h1>
      <ul>
        <li>Task 1</li>
        <li>Task 2</li>
        <li>Task 3</li>
      </ul>
    </div>
  );
}

When the above component is rendered, React creates a corresponding Virtual DOM structure based on the JSX code. The Virtual DOM would look like the following:

{
  type: 'div',
  props: {
    children: [
      {
        type: 'h1',
        props: {
          children: 'Todo List'
        }
      },
      {
        type: 'ul',
        props: {
          children: [
            {
              type: 'li',
              props: {
                children: 'Task 1'
              }
            },
            {
              type: 'li',
              props: {
                children: 'Task 2'
              }
            },
            {
              type: 'li',
              props: {
                children: 'Task 3'
              }
            }
          ]
        }
      }
    ]
  }
}

In the Virtual DOM, each HTML element and its attributes are represented as plain JavaScript objects. The component hierarchy and the relationships between elements are maintained through nested objects.

Difference Between Virtual DOM and Real DOM

Difference Between Virtual DOM and Real DOM

Virtual DOM and Real DOM are two concepts used in web development to manage and update the user interface of a web application. Here are the key differences between Virtual DOM and Real DOM:

AspectVirtual DOMReal DOM
DefinitionLightweight in-memory copy of the Real DOM maintained by frameworks like React.Actual live HTML DOM in the web browser representing the current state of the webpage.
PerformanceFaster updates compared to direct manipulation of the Real DOM.Slower updates due to direct manipulation and immediate repaints
RenderingRendering is done in-memory, allowing efficient updates before applying changes to the Real DOM.Rendering directly applied to the browser DOM.
Direct ManipulationDevelopers work with an abstracted Virtual DOM, which is more intuitive.Developers directly interact with the Real DOM, which can be error-prone.
Dependency on FrameworkOften associated with JavaScript libraries/frameworksIndependent of any specific library or framework.

Virtual DOM acts as a lightweight and efficient intermediary layer between the application’s state changes and the actual browser DOM. By minimizing direct manipulation of the Real DOM and optimizing updates, it enhances the overall performance and user experience of web applications.

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Conclusion

In conclusion, the Document Object Model (DOM) is an essential concept in React, allowing developers to interact with and manipulate web pages. React introduced the Virtual DOM, a lightweight representation of the actual DOM, which significantly improves performance by reducing unnecessary re-rendering. 

By comparing the Virtual DOM with the Real DOM, we understand that the former is more efficient in updating only the necessary components. Additionally, installing the React Router DOM enables seamless navigation and routing in React applications. Understanding the DOM and its relationship with React’s Virtual DOM is crucial for building efficient and dynamic web applications.

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About the Author

Techical Research Analyst - Front End Development

As a Technical Research Analyst, Kislaya specializes in Front End Development. He is a Full Stack Developer, known for crafting scalable architectures and user-centric interfaces. He has a massive international client base and is an expert in cloud computing, Linux, and Java Script, personifying a commitment to quality and information sharing.