React

React is a framework that works with Javascript to render dynamic page content. It maintains a state variable for each dynamic element that are controlled using components made using classes or functions and hooks.

This competency area includes integrating framework knowledge with business logic, creating and running comprehensive unit tests on the React application, Debugging, Hooks, among others. 

Key Competencies:

1. Business Logic - Integrate framework knowledge with business logic.
2. Unit Testing - Creating and running comprehensive unit tests on the React application.
3. Debugging React - Identifying problems based on error messages, deep knowledge of syntax and semantics, knowledge of common errors in renders, state management, etc.
4. Hooks (useEffect with dependencies, useLayoutEffect, custom hooks) - Using useEffect with dependencies to limit new renders, use useLayoutEffect and create and use custom hooks.
5. Error Boundaries - Catch unexpected errors and display a fallback UI.
6. React Context API - Create and use context to pass information to descendants