Unlock hundreds more features
Save your Quiz to the Dashboard
View and Export Results
Use AI to Create Quizzes and Analyse Results

OR
Sign inSign in with Facebook
Sign inSign in with Google
Quizzes > Quizzes for Business > Technology

React Fundamentals Knowledge Test Quiz

Assess Your React Basics & Core Concepts

Difficulty: Moderate
Questions: 20
Learning OutcomesStudy Material
Colorful paper art promoting a quiz on React Fundamentals Knowledge Test.

Are you ready to challenge your React fundamentals and sharpen your development skills? This interactive React Knowledge Assessment Quiz guides learners through topics like components, state, and lifecycle methods. Whether diving into React basics or reinforcing your UI building expertise, this quiz provides instant feedback and clear explanations. Educators and students alike can customise every question using our editor - a perfect way to tailor content for any curriculum. Explore more IT Fundamentals Knowledge Quiz options or browse all quizzes for further practice.

Which syntax extension allows writing HTML-like code within React components?
HTML
TSX
JSX
Babel
JSX is a syntax extension for JavaScript that lets developers write HTML-like code in React components. It must be transpiled by tools like Babel before browsers can execute it.
How do you embed a JavaScript expression inside JSX?
Using quotes " "
Using parentheses ( )
Using angle brackets < >
Using curly braces { }
In JSX, curly braces { } are used to embed JavaScript expressions directly within markup. This allows dynamic values to be rendered alongside static content.
How do you define a simple functional component in React?
class MyComponent extends React { render() {} }
function MyComponent() { return
Hello
; }
React.createElement(MyComponent)
const MyComponent =
Hello
A functional component in React is defined as a function that returns JSX. The function name must start with a capital letter to be recognized as a component.
What file extension is commonly used for files that contain JSX syntax?
.html
.js
.json
.jsx
.jsx is the conventional file extension for JavaScript files that include JSX syntax. It signals to tools and editors that the file contains React markup.
How do you import the React library at the top of a component file?
#include
import React from 'react';
using React;
require('react');
In modern React code, you import the React library using ES6 module syntax: import React from 'react';. This makes React's APIs available in the file.
How do you correctly update the state of a class component in React?
setState({ key: value });
this.state.key = value;
this.setState({ key: value });
updateState({ key: value });
In class components, state updates must be done through this.setState, which schedules a re-render. Directly modifying this.state does not trigger a re-render.
Which React Hook is used to add state to functional components?
useEffect
useContext
useState
useReducer
useState is the built-in Hook that lets you add state variables to functional components. It returns a state value and a function to update it.
How do you attach a click event handler to a button in JSX?
onClick={handleClick}
handleClick={() => click}
onClick="handleClick()"
onclick={handleClick}
JSX event handlers use camelCase syntax and take a function reference inside curly braces. onClick={handleClick} correctly attaches the handler.
What is the primary purpose of the "key" prop when rendering lists in React?
To pass data to a child component
To help React identify which items have changed
To trigger list re-renders manually
To apply CSS styles to list items
Keys are unique identifiers for list items that help React's diffing algorithm determine which items have changed, been added, or removed.
Which property in a React component holds the children passed between its opening and closing tags?
state.children
this.children
props.content
props.children
Any nested elements or components placed between a component's tags are available on props.children. Developers can render or iterate over them inside the component.
Which lifecycle method is called immediately after a React component is mounted?
componentDidMount
componentDidUpdate
componentWillMount
render
componentDidMount runs once after the component is inserted into the DOM. It is commonly used for initializing data or setting up subscriptions.
Which React Hook should you use to perform side effects in a functional component?
useState
useEffect
useContext
useMemo
useEffect runs after render and is designed for side effects like data fetching or manual DOM manipulation. Dependencies control when the effect re-runs.
How do you create a controlled input component in React?
Use defaultValue prop without onChange
Attach a ref and manually read the value
Set the input's value prop to state and update state in onChange
Omit the value prop entirely
A controlled component ties its value prop to React state and updates that state on every onChange call. This gives full control of user input to React.
In React, how do you prevent the default action of an event inside an event handler?
Call event.preventDefault()
Return false from the handler
Use stopPropagation()
Set event.default to false
Calling event.preventDefault() stops the browser's default behavior for that event. Returning false does not have this effect in React.
Which lifecycle method is used to catch errors in a component's child tree?
componentDidCatch
getDerivedStateFromProps
componentDidMount
componentWillUnmount
componentDidCatch is an error boundary method that catches exceptions in the render phase of child components. It can be used to log errors or display a fallback UI.
What is the correct way to initialize a reducer in React using Hooks?
const [state, dispatch] = useReducer();
const [state, dispatch] = useReducer(reducer, initialState);
const [state, dispatch] = useReducer(reducer);
const [reducer, state] = useReducer(initialState);
useReducer takes exactly two arguments: the reducer function and the initial state. It returns the current state paired with a dispatch function.
Which method helps avoid unnecessary re-renders by memoizing a functional component?
useCallback
useMemo
PureComponent
React.memo
React.memo is a higher-order function that wraps a functional component and memoizes its rendered output. It prevents re-renders when props haven't changed.
What is a Higher-Order Component (HOC) in React?
A component that handles form submissions
A function that takes a component and returns a new component
A component that wraps multiple children
A hook for sharing logic
A Higher-Order Component is a pattern where a function takes an existing component and returns an enhanced one. It's used for code reuse and injecting additional props or behavior.
What feature does React Suspense provide when used with React.lazy?
Catches errors in async components
Displays a fallback UI while lazy-loaded components load
Optimizes component re-renders
Manages global application state
React Suspense allows you to specify a fallback UI that will be shown while a lazily loaded component (via React.lazy) is still loading. It simplifies code-splitting.
Which React Hook allows optimizing expensive computations by memoizing values?
useLayoutEffect
useMemo
useCallback
useEffect
useMemo caches the result of a computation between renders unless its dependency array changes. This reduces the cost of heavy calculations on each render.
0
{"name":"Which syntax extension allows writing HTML-like code within React components?", "url":"https://www.quiz-maker.com/QPREVIEW","txt":"Which syntax extension allows writing HTML-like code within React components?, How do you embed a JavaScript expression inside JSX?, How do you define a simple functional component in React?","img":"https://www.quiz-maker.com/3012/images/ogquiz.png"}

Learning Outcomes

  1. Apply JSX syntax for dynamic UI creation
  2. Identify and differentiate React component types
  3. Manage state and props effectively in apps
  4. Demonstrate event handling within components
  5. Evaluate component lifecycle methods
  6. Troubleshoot common React errors

Cheat Sheet

  1. Master JSX Syntax - JSX is the secret sauce that lets you write HTML-like code right inside your JavaScript, making your UI development feel like magic. Always remember to properly close your tags and switch to camelCase attributes, like className instead of class, to avoid sneaky bugs. Practicing these small rules will make your code cleaner and your life easier. React JSX Guide
  2. Understand Functional vs Class Components - React offers two main component styles: functional for quick, presentation-focused pieces and class for more heavy-lifting with state and lifecycle methods. Knowing when to pick each one helps you write clearer, more efficient code. Dive into their differences to level up your component game. React Lifecycle Methods & Hooks Guide
  3. Manage State and Props - State lets your components remember dynamic data, while props pass that data down to child components like a magic relay race. Mastering the flow between state and props is key to building interactive apps that actually respond to user actions. Practice by building a simple counter or todo list to see them in action. Deep Dive into State & Props
  4. Implement Event Handling - User clicks, hovers, and form submissions are where the fun happens - React handles them with camelCase props like onClick and onChange. Pass in functions that update state or trigger side effects to make your UI truly interactive. Try wiring up a button that changes color on each click! React Event Handling Examples
  5. Explore Lifecycle Methods - Class components come with lifecycle hooks such as componentDidMount, componentDidUpdate, and componentWillUnmount to control behavior at different stages. Whether you need to fetch data when a component appears or clean up timers before it disappears, these methods are your toolkit. Understanding them unlocks advanced patterns. Lifecycle Methods Explained
  6. Utilize React Hooks - Hooks like useState and useEffect let you manage state and side effects right inside functional components, trimming boilerplate and boosting readability. Think of useEffect as the modern alternative to lifecycle methods and useState as your local memory. Experiment with them to see how they simplify logic. Hooks in React
  7. Practice Conditional Rendering - Want to show a loader, an error message, or a secret bonus level? Use JavaScript expressions or ternary operators within JSX to render content based on state or props. Conditional rendering keeps your UI flexible and user-friendly. Challenge yourself by creating a login form that displays different components for success or failure. JSX Conditional Rendering Examples
  8. Assign Unique Keys in Lists - When rendering lists, React uses keys to track each item's identity, helping it optimize updates and avoid re-rendering the whole list. Always assign stable, unique keys - such as IDs instead of array indexes - to prevent weird UI glitches. This tiny habit yields big performance gains. Guide to Keys in React
  9. Troubleshoot Common React Errors - From "Missing key" warnings to syntax slip-ups in JSX, every developer hits roadblocks. Learning to read error messages and trace them back to your code is like unlocking a secret superpower. Collect and fix your most frequent mistakes to build confidence. Common JSX Errors & Fixes
  10. Leverage React Fragments - Fragments allow you to group multiple elements without adding extra nodes to the DOM, keeping your markup lean and tidy. Use <React.Fragment> or its shorthand <></> when you need to return siblings from a component. Cleaner trees, happier browsers! Using React Fragments
Make a Quiz (FREE) Copy & Edit This Quiz Create a Quiz with AI

Technology Quizzes

Powered by: Quiz Maker