Loading... Login Loading... Register

React Basics Quiz

Want to learn more than this quiz offers you? Have a look at my Frontend web development courses.

Create an account and save your quiz results

Login and save your results

First Name *

Last Name *

Email *

Password *

Confirm Password *

I agree to the Terms of Service & Privacy Policy.

Add me to your newsletter.

Question 1/15

Which method should be overridden to return a React element from a class component?

Select your answer

render()

componentDidMount()

getInstance()

setState()

Question 2/15

What is the significance of 'props' in React?

Select your answer

Props are inputs to a React component and are passed from a parent component.

Props hold the state of components internally.

Props are immutable and therefore cannot be passed between components.

Props are the same as a component's local variables.

Question 3/15

What is the purpose of keys in React lists?

Select your answer

To give each element in the list a stable identity.

To decrypt encrypted state data.

To automatically generate unique IDs.

To enable CSS styling for list elements.

Question 4/15

Which method is used to update state in a class component?

Select your answer

changeState()

updateState()

assignState()

setState()

Question 5/15

What is JSX in React?

Select your answer

A JavaScript library for managing forms.

A framework for building REST APIs.

A style sheet language used for describing presentation.

A syntax extension for JavaScript that looks similar to XML or HTML.

Question 6/15

What does the constructor method do in a React class component?

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = { count: 0 };
  }

  render() {
    return <div>{this.state.count}</div>;
  }
}

Select your answer

Renders the HTML content to the page.

Initializes the state and binds event handlers.

Defines the styles for the component.

Calls external APIs before rendering.

Question 7/15

How do you declare a functional component in React?

function MyComponent() {
  return <div>Hello World</div>;
}

Select your answer

By using a 'service-worker.js' file.

By defining a JavaScript function that returns a React element.

By instantiating a new object.

By extending 'React.Component' and defining a 'render' method.

Question 8/15

Which statement about 'useState' hook is true?

Select your answer

It synchronously updates state but does not trigger a re-render.

It provides only a state read function and no setters.

It lets you add state to function components and returns the current state and a function to update it.

It is used only in class components.

Question 9/15

Why is it important to use keys when rendering lists in React?

Select your answer

They allow for the automatic update of state values.

They ensure that list elements are styled correctly.

They enforce security protocols.

They help identify elements to improve performance during re-renders.

Question 10/15

How do you handle events in React?

Select your answer

By writing inline event handlers with HTML attributes such as 'onclick'.

By using the 'bind' attribute in HTML.

By handling only JavaScript's default events without any React involvement.

By defining event handlers in JavaScript and passing them as props to the elements.

Question 11/15

What does the 'return' statement do in a React component?

function Greeting() {
  return <h1>Hello, world!</h1>;
}

Select your answer

Executes a function upon rendering.

Immediately stops executing the component function.

Defines the UI to be rendered to the DOM.

Only works in class components.

Question 12/15

What is the difference between state and props?

Select your answer

State and props serve the same purpose in React.

State is internal and managed within the component, while props are external and passed to the component.

State can only hold strings, but props can hold objects.

State is a class-based component feature, while props are exclusive to functional components.

Question 13/15

What is the purpose of componentDidMount lifecycle method?

Select your answer

To initialize state before rendering.

To update the component state after every render.

To handle event bindings only.

To execute code after the component is inserted into the DOM.

Question 14/15

What is a React component?

Select your answer

A bundle of functions that performs HTTP requests.

An HTML element that is used once in a React application.

A CSS file that styles the user interface.

A JavaScript function or class that optionally accepts inputs and returns a React element.

Question 15/15

Which hook in React function components is used to replace componentDidMount?

Select your answer

useReducer

useState

useContext

useEffect

Your Results

You did not answer any questions correctly.

Your Answers

Question 1/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which method should be overridden to return a React element from a class component?

Available answers

render()

componentDidMount()

getInstance()

setState()

The

render()

method is required for class components and should be overridden to return the React elements dictating what gets rendered to the DOM. The elements in the

render()

method directly represent the rendered interface.

Question 2/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the significance of 'props' in React?

Available answers

Props are inputs to a React component and are passed from a parent component.

Props hold the state of components internally.

Props are immutable and therefore cannot be passed between components.

Props are the same as a component's local variables.

Props (short for properties) are inputs to a component typically passed from a parent component. They are used to pass data and event handlers from a parent to a child component. Props are immutable, meaning a component should not change them.

Question 3/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the purpose of keys in React lists?

Available answers

To give each element in the list a stable identity.

To decrypt encrypted state data.

To automatically generate unique IDs.

To enable CSS styling for list elements.

In React, keys help identify which items have changed, been added, or been removed. Keys should be given to the elements inside the array to give the elements a stable identity:

const items = items.map((item) => <li key={item.id}>{item.name}</li>)

Question 4/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which method is used to update state in a class component?

Available answers

changeState()

updateState()

assignState()

setState()

In class components, you should use the 'setState()' method to update the component's state. This method ensures the component is re-rendered with the updated state and handles updating the state asynchronously.

Question 5/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is JSX in React?

Available answers

A JavaScript library for managing forms.

A framework for building REST APIs.

A style sheet language used for describing presentation.

A syntax extension for JavaScript that looks similar to XML or HTML.

JSX is a syntax extension for JavaScript that resembles XML or HTML. It is used within React to describe what the UI should look like. Rather than separating logic and presentation as in some traditional approaches, JSX integrates HTML with JavaScript code, making it easier to visualize the structure of the UI.

Question 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

What does the constructor method do in a React class component?

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = { count: 0 };
  }

  render() {
    return <div>{this.state.count}</div>;
  }
}

Available answers

Renders the HTML content to the page.

Initializes the state and binds event handlers.

Defines the styles for the component.

Calls external APIs before rendering.

In React class components, the 'constructor' method is used for initializing state and, if necessary, binding methods to 'this'. The constructor is called before the component is mounted and is a good place to set up any initial state.

Question 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

How do you declare a functional component in React?

function MyComponent() {
  return <div>Hello World</div>;
}

Available answers

By using a 'service-worker.js' file.

By defining a JavaScript function that returns a React element.

By instantiating a new object.

By extending 'React.Component' and defining a 'render' method.

In React, you can declare a functional component by defining a JavaScript function that returns a JSX element. This function receives 'props' as an argument and returns the UI representation.

Question 8/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which statement about 'useState' hook is true?

Available answers

It synchronously updates state but does not trigger a re-render.

It provides only a state read function and no setters.

It lets you add state to function components and returns the current state and a function to update it.

It is used only in class components.

The 'useState' hook lets you add state to function components. It returns an array containing the current state and a function to update that state, allowing functional components to manage state without converting them to class components.

Question 9/15

😊 Your answer was correct 🙁 Your answer was incorrect

Why is it important to use keys when rendering lists in React?

Available answers

They allow for the automatic update of state values.

They ensure that list elements are styled correctly.

They enforce security protocols.

They help identify elements to improve performance during re-renders.

Keys are important in React because they help the library identify elements when updating the UI, producing better performance by reducing re-rendering times. They provide a way to keep elements' stable identities across renders.

Question 10/15

😊 Your answer was correct 🙁 Your answer was incorrect

How do you handle events in React?

Available answers

By writing inline event handlers with HTML attributes such as 'onclick'.

By using the 'bind' attribute in HTML.

By handling only JavaScript's default events without any React involvement.

By defining event handlers in JavaScript and passing them as props to the elements.

In React, events are handled using camelCase syntax. Instead of using HTML attributes like 'onclick', you pass a function as the event handler in JSX:

<button onClick={handleClick}>Click Me</button>

Question 11/15

😊 Your answer was correct 🙁 Your answer was incorrect

What does the 'return' statement do in a React component?

function Greeting() {
  return <h1>Hello, world!</h1>;
}

Available answers

Executes a function upon rendering.

Immediately stops executing the component function.

Defines the UI to be rendered to the DOM.

Only works in class components.

In a React component, the 'return' statement declares what JSX, or combination of React elements, should be displayed in the UI. This forms the basis of how the component renders itself to the DOM.

Question 12/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the difference between state and props?

Available answers

State and props serve the same purpose in React.

State is internal and managed within the component, while props are external and passed to the component.

State can only hold strings, but props can hold objects.

State is a class-based component feature, while props are exclusive to functional components.

In React, 'state' is an internal construct maintained by the component itself, used for rendering dynamic data and changes within the component. 'Props', on the other hand, are data passed to the component from a parent for use within the child component.

Question 13/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the purpose of componentDidMount lifecycle method?

Available answers

To initialize state before rendering.

To update the component state after every render.

To handle event bindings only.

To execute code after the component is inserted into the DOM.

The 'componentDidMount' method is invoked immediately after a component is mounted. This is the best place to initiate network requests, set timers, or directly interact with the DOM.

Question 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is a React component?

Available answers

A bundle of functions that performs HTTP requests.

An HTML element that is used once in a React application.

A CSS file that styles the user interface.

A JavaScript function or class that optionally accepts inputs and returns a React element.

In React, a component is a JavaScript function or class that optionally accepts inputs (known as 'props') and returns a React element that describes how a section of the UI should appear. Components can be either stateful or stateless, and they can be composed within other components.

Question 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which hook in React function components is used to replace componentDidMount?

Available answers

useReducer

useState

useContext

useEffect

In React function components, the 'useEffect' hook can be used to perform side effects similar to the 'componentDidMount' lifecycle method in class components. You can use 'useEffect' to manage tasks like data fetching or directly interacting with the DOM.