Reconciliation is the process through which React updates the DOM to match the new state of the application. When a component’s state or props change, React creates a new virtual DOM tree and compares it with the previous virtual DOM snapshot. This comparison process is called diffing.

React uses an efficient algorithm to identify the minimal number of changes needed and updates only the parts of the real DOM that actually changed. This selective update process improves performance and makes React applications faster.

Here’s how Reconciliation works step-by-step:

1. State/Props Change: A change triggers re-rendering of the component.
2. Virtual DOM Creation: A new virtual DOM is created based on the updated data.
3. Diffing Algorithm: React compares the new virtual DOM with the old virtual DOM.
4. Efficient Updates: React calculates the most efficient way to update the real DOM and applies only those updates.

Key Points:

• React assumes elements of different types (like <div> and <span>) result in a completely different tree and thus destroys the old DOM node and builds a new one.
• React uses keys to optimize reconciliation when rendering lists. Keys help React identify which items have changed, been added, or been removed.

Why is Reconciliation Important?

• Performance: It prevents unnecessary DOM updates.
• Smooth UI Updates: It ensures the UI feels fast and responsive.
• Developer Efficiency: Developers don’t need to manually handle DOM operations.

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