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 understanding basic routing, rendering elements, state management, handling events, among others. 

Key Competencies:

1. Basic Routing - Matching request paths to their respective components.
2. Rendering Elements - Generating dynamic HTML elements such as lists or forms.
3. State Management (Internal Component State) - Creating and updating state values in class components.
4. Handling Events - Execute functions and Update state variables when an event occurs.
5. ES6 and JavaScript - Creating functions including arrow functions to manipulate data and its display as page elements.
6. Form Validation - Validating form data against rules before accepting input and alerting the user with an error message when validation fails.