ReactJS Fundamentals: Essential Concepts Quiz Quiz

Assess your knowledge of ReactJS basics with these key questions covering core concepts like components, state, hooks, and routing. Perfect for anyone starting out in modern frontend development.

1. Main Purpose of React

   What is React mainly used for in frontend development?

   1. Building user interfaces (UI) using components
   2. Writing backend APIs
   3. Managing databases
   4. Server-side scripting

   Explanation: React is primarily used for creating user interfaces by composing them from reusable components. Managing databases and server-side scripting are handled by other technologies. Writing backend APIs is also not the main focus of React.

2. Understanding JSX

   What is JSX in the context of React?

   1. JavaScript syntax that lets you write HTML-like code
   2. A database query language
   3. A RESTful API specification
   4. A type of CSS preprocessor

   Explanation: JSX allows developers to write HTML-like code within JavaScript, making UI code more readable and intuitive. It is not a CSS preprocessor or API standard, nor is it used for databases.

3. Managing State in React

   Which React hook is commonly used to manage state within a functional component?

   1. useMemo()
   2. useReducer()
   3. useRef()
   4. useState()

   Explanation: useState() is the standard hook for introducing and managing state in functional components. useRef() is for referencing DOM nodes, useMemo() optimizes performance, and useReducer() is for complex state logic.

4. React Hook for Side Effects

   Which hook is used in React to handle side effects such as data fetching or timers?

   1. useSelector()
   2. useEffect()
   3. useCallback()
   4. useLayoutEffect()

   Explanation: useEffect() is designed for handling side effects in React components. useSelector() relates to state management libraries, useCallback() optimizes functions, and useLayoutEffect() is for syncing layout side effects.

5. Defining a Component

   What is a component in React?

   1. A styling method
   2. A third-party library
   3. A global configuration file
   4. A reusable piece of UI

   Explanation: Components in React encapsulate and reuse UI pieces, improving code organization. They are not files, styling methods, or external libraries.

6. Understanding Props

   In React, what are props?

   1. CSS styling rules
   2. Commands to run scripts
   3. Methods for updating state
   4. Data passed from parent to child components

   Explanation: Props allow parent components to send data to their children, enabling dynamic and reusable components. They are not scripts, state methods, or CSS rules.

7. Purpose of the Virtual DOM

   What is the Virtual DOM in React?

   1. A browser extension
   2. A type of web server
   3. A lightweight copy of the real DOM React uses to improve performance
   4. A way to write server code

   Explanation: The Virtual DOM is a technique to efficiently update the UI by comparing changes before updating the real DOM. It is not a server, code-writing tool, or browser extension.

8. Conditional Rendering in React

   How can you conditionally render UI elements in React?

   1. By modifying the HTML file directly
   2. Using database triggers
   3. Applying inline CSS only
   4. Using logical operators or ternary (? :) expressions

   Explanation: Conditional rendering in React is typically done with logical (&&) or ternary (? :) operators in JSX. Modifying HTML directly or using CSS and database triggers do not control React component rendering.

9. Accessing Context in React

   Which hook allows a React component to access context values provided by a provider?

   1. useParams()
   2. useContext()
   3. useEffect()
   4. useReducer()

   Explanation: useContext() is the React hook for subscribing to context values. useEffect() is for side effects, useReducer() handles state logic, and useParams() is associated with routing.

10. Role of React Router

    What is React Router primarily used for in a React application?

    1. Creating animated UI
    2. Optimizing performance
    3. Navigation between pages in a React app
    4. Styling components

    Explanation: React Router enables single-page applications to have navigation and route different views. It does not handle styling, UI animation, or pure performance optimizations.