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Ankush Goyal
Ankush Goyal

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ReactJs: Virtual DOM

The Virtual DOM (VDOM) is a concept used in React to optimize and manage updates to the user interface. Here's how it works:

What is the Virtual DOM?

The Virtual DOM is a lightweight, in-memory representation of the actual DOM. It is a JavaScript object that React uses to keep track of changes in the UI.

How Does It Work?

  1. Initial Render: When a React component is rendered for the first time, a Virtual DOM tree is created that mirrors the structure of the actual DOM.
  2. State Changes: When the state of a component changes, React creates a new Virtual DOM tree.
  3. Diffing Algorithm: React compares the new Virtual DOM tree with the previous one using a process called "diffing." It identifies the changes (differences) between the two trees.
  4. Reconciliation: React then updates only the parts of the actual DOM that have changed, rather than re-rendering the entire DOM. This process is called "reconciliation."

Benefits

  • Performance: By minimizing direct manipulation of the actual DOM, which is slow, the Virtual DOM improves performance.
  • Efficiency: React's diffing algorithm ensures that only the necessary updates are made, making the UI updates more efficient.

Example

Consider a simple example where a button click updates a counter:

import React, { useState } from 'react';

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

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>Click me</button>
    </div>
  );
}

export default Counter;
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In this example, each time the button is clicked, the state changes, and React updates the Virtual DOM. It then compares the new Virtual DOM with the previous one, identifies the change in the counter value, and updates only the relevant part of the actual DOM.


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