React Virtual DOM: Syntax, Usage, and Examples

React virtual dom is a lightweight representation of the actual DOM, allowing React to update the UI efficiently. Instead of modifying the real DOM directly, React makes changes to the virtual DOM first, then updates only the necessary parts of the real DOM.

How to Use the React Virtual DOM

React automatically manages the virtual DOM behind the scenes, so you don’t need to configure it manually. However, understanding how it works can help you write more efficient components.

How React Uses the Virtual DOM

1. React creates a virtual DOM tree that mirrors the actual DOM.
2. When state or props change, React updates the virtual DOM instead of the real DOM.
3. React compares the updated virtual DOM to the previous version using a process called "reconciliation."
4. It finds the differences (or "diffs") and updates only the necessary parts of the real DOM.

Example of React Virtual DOM in Action

import { useState } from "react";

function Counter() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

In this example, when setCount updates count, React updates only the <p> element instead of re-rendering the entire page.

When to Use the React Virtual DOM

Optimizing Performance

React virtual dom makes updates more efficient than directly modifying the real DOM. This is especially useful in complex applications where frequent updates happen.

Reducing Repaints and Reflows

Since React batches changes and updates only the necessary parts of the real DOM, it minimizes browser repaints and reflows, which improves performance.

Managing Dynamic UI Updates

For applications with frequent UI updates, such as chat apps, dashboards, or games, the virtual DOM ensures smooth rendering without unnecessary redraws.

Examples of React Virtual DOM in Action

Handling Multiple Updates Efficiently

If you update multiple states within an event handler, React batches them to minimize re-renders.

import { useState } from "react";

function App() {
  const [count, setCount] = useState(0);
  const [text, setText] = useState("");

  const handleClick = () => {
    setCount(count + 1);
    setText("Updated!");
  };

  return (
    <div>
      <p>Count: {count}</p>
      <p>Message: {text}</p>
      <button onClick={handleClick}>Update</button>
    </div>
  );
}

Here, React updates both the count and text changes efficiently in a single render.

Conditional Rendering with Virtual DOM

React avoids unnecessary DOM updates when rendering conditionally.

function Message({ isVisible }) {
  return (
    <div>
      {isVisible ? <p>Hello, World!</p> : <p>Goodbye, World!</p>}
    </div>
  );
}

Only the relevant paragraph updates, instead of re-rendering the entire component tree.

Lists and Virtual DOM Efficiency

When rendering lists, React uses the virtual DOM to update only the changed items.

function ItemList({ items }) {
  return (
    <ul>
      {items.map((item, index) => (
        <li key={index}>{item}</li>
      ))}
    </ul>
  );
}

Using key helps React identify which items changed, reducing unnecessary re-renders.

Learn More About the React Virtual DOM

What is the Virtual DOM in React?

The virtual dom in react is a JavaScript representation of the real DOM. React uses it to determine the most efficient way to update the UI.

React Virtual DOM vs Shadow DOM

The shadow DOM is a browser feature that encapsulates styles and elements, preventing them from affecting the rest of the page. The React virtual dom, on the other hand, is a performance optimization technique that helps React update the UI efficiently.

Advantages of Virtual DOM in React

• Faster Updates: React batches updates and modifies only the necessary parts of the real DOM.
• Better Performance: Reduces unnecessary reflows and repaints.
• Easier Debugging: Allows React to track state changes and component updates efficiently.

React Virtual DOM Explained in Simple Terms

Think of the virtual DOM as a "draft" of the real DOM. React first makes changes to this draft, then figures out the minimal updates needed before applying them to the actual DOM. This reduces unnecessary changes and speeds up performance.