What is Reconciliation in React

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Reconciliation in React is the process of updating the user interface (UI) to reflect the changes in the underlying data. It is a key feature of React that efficiently updates only the necessary components, rather than re-rendering the entire UI.

React uses a virtual DOM (VDOM) to perform reconciliation. When there is a change in the state or props of a component, React creates a new VDOM representation of the component and compares it with the previous VDOM. This comparison is done in a process called diffing.

During diffing, React identifies the differences between the new and previous VDOM and updates only the necessary parts of the UI. This optimization helps in improving the performance of React applications.

Here is an example of how reconciliation works in React using JavaScript and HTML:

// JavaScript code
class Counter extends React.Component {
constructor(props) {
super(props);
this.state = { count: 0 };
}
incrementCount() {
this.setState({ count: this.state.count + 1 });
}
render() {
return (
<div>
<h1>Counter: {this.state.count}</h1>
<button onClick={() => this.incrementCount()}>Increment</button>
</div>
);
}
}
ReactDOM.render(<Counter />, document.getElementById('root'));


<!-- HTML code -->
<!DOCTYPE html>
<html>
<head>
<title>Reconciliation in React</title>
</head>
<body>
<div id="root"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.1/umd/react.development.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.1/umd/react-dom.development.js"></script>
<script src="your-javascript-file.js"></script>
</body>
</html>

In this example, we have a Counter component that maintains a count state. When the Increment button is clicked, the incrementCount method is called, which updates the count state using setState. React then performs reconciliation to update only the necessary parts of the UI, in this case, the Counter value.

Note: Replace your-javascript-file.js with the actual filename where you save the JavaScript code.