What is reconciliation in React?

Reconciliation is React’s process of comparing the Virtual DOM tree with a new version and updating only the parts that changed.

⚙️ Example

const el1 = <h1>Hello</h1>;
const el2 = <h1>Hello, World!</h1>;

React compares both elements, finds the text difference, and updates only that node in the real DOM.

🧠 Key Principles

• Same type elements → update attributes only.
• Different type → replace the entire subtree.
• Lists → keys help React match existing elements.

✅ Reconciliation makes React’s rendering O(n), not O(n²).