Prep Plan for Offline Drive

1. Why React?

• Key Concepts to Cover:
  • React's component-based architecture and reusability.
  • React's declarative programming model for building UIs.
  • Comparison with traditional approaches (imperative vs declarative).
  • Unidirectional data flow and how React improves app performance.
  • JSX: How it simplifies writing UI with JavaScript.
• Practice Questions:
  • Why is React considered a popular library for building user interfaces?
  • What is the difference between imperative and declarative programming? Why does React favor declarative?
  • Explain how components help in reusability and modularity in large-scale applications.
• Task:
  • Write a simple React component that displays a list of items passed as props.
  • Build a small React application that uses state and props to manage data flow in a component hierarchy.
  • Write a comparison between React and a traditional approach like jQuery for building interactive UIs.

2. Virtual DOM (vDOM)

• Key Concepts to Cover:
  • What is the Virtual DOM (vDOM)?
  • How React uses the vDOM to improve performance.
  • Difference between the vDOM and the real DOM.
  • How React updates the vDOM, compares changes, and then updates the actual DOM.
• Practice Questions:
  • What is the Virtual DOM in React, and how does it work?
  • Why does the vDOM make React faster than directly manipulating the real DOM?
  • Explain the process of updating the vDOM when a component's state changes.
• Task:
  • Write a simple React app and explain what happens to the vDOM and real DOM when the state is updated.
  • Create a demo showing how React uses the vDOM to reduce the number of manipulations on the real DOM.

3. Reconciliation

• Key Concepts to Cover:
  • What reconciliation is and how React decides what changes need to be applied to the DOM.
  • How React compares the current vDOM tree with the previous one.
  • The efficiency of reconciliation: Only the necessary changes are made to the DOM.
  • Key importance for optimizing lists: Why React needs key props for elements in lists.
• Practice Questions:
  • What is reconciliation in React? How does React efficiently update the DOM using this process?
  • Explain how React uses keys during reconciliation and why they are important.
  • What happens when keys are missing or incorrectly used in a list of elements?
• Task:
  • Write a React app where a list of items is rendered and update the list dynamically. Use key props and explain how React handles the reconciliation process.
  • Write a function that demonstrates the incorrect usage of keys and explain the performance consequences.

4. Diffing Algorithm

• Key Concepts to Cover:
  • What is the Diffing Algorithm and how React uses it to determine the minimum set of changes needed to update the DOM.
  • The O(n) complexity of the algorithm, which makes it efficient even for large applications.
  • How the diffing algorithm compares elements at the same level in the tree to avoid unnecessary updates.
  • React's heuristics: Element-by-element comparison and handling child components.
• Practice Questions:
  • What is the Diffing Algorithm in React, and how does it contribute to the efficiency of the vDOM?
  • How does React’s Diffing Algorithm ensure optimal performance when re-rendering components?
  • What are the key heuristics React follows while diffing two trees?
• Task:
  • Implement a small React app and explain, step-by-step, how the Diffing Algorithm works during a re-render when state changes.
  • Demonstrate how React's Diffing Algorithm handles a scenario where sibling nodes are reordered or removed.