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React Basics Quiz

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Question 1/15

What is JSX in React?

Select your answer

A JavaScript library for managing forms.

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

A framework for building REST APIs.

A style sheet language used for describing presentation.

Question 2/15

How do you create a class-based component in React?

class MyComponent extends React.Component {
  render() {
    return <div>Hello World</div>;
  }
}

Select your answer

By using the 'class' keyword and extending 'React.Component'.

By creating an HTMLElement instance.

By using the 'function' keyword and returning a string.

By using an anonymous function expression.

Question 3/15

Which of these statements about state in React is true?

Select your answer

State is the same as props.

State is static and does not update once the component is mounted.

State should be mutated directly for updates.

State is a way to hold dynamic data and can influence the output of a component's render function.

Question 4/15

How does React update the user interface efficiently?

Select your answer

By sending AJAX requests every few seconds to refresh the page.

By using a virtual DOM to track changes and update only the affected parts of the DOM.

By directly manipulating the DOM every time a change occurs.

By using a single HTML file that is reloaded every change.

Question 5/15

How can you bind functions to the correct context in React class components?

Select your answer

By using arrow functions or binding them in the constructor.

By using the 'delay' prop on method calls.

By creating new instances inside render.

By declaring them outside the component scope.

Question 6/15

What is a React component?

Select your answer

A CSS file that styles the user interface.

A bundle of functions that performs HTTP requests.

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

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

Question 7/15

How do you write comments in JSX?

Select your answer

Comments are not allowed in JSX.

For block comments, surround the code with /* comments */.

Use hashtags like #comment.

Use curly braces and an asterisk: {/* Your comment here */}

Question 8/15

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

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

Select your answer

Immediately stops executing the component function.

Only works in class components.

Defines the UI to be rendered to the DOM.

Executes a function upon rendering.

Question 9/15

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

Select your answer

setState()

componentDidMount()

render()

getInstance()

Question 10/15

How do you handle events in React?

Select your answer

By using the 'bind' attribute in HTML.

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

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

Can React handle asynchronous operations within components?

Select your answer

No, React components cannot perform asynchronous operations.

Yes, but only in class components using setState.

Yes, by using lifecycle methods or hooks such as useEffect.

Yes, but only with external libraries, as React does not support it natively.

Question 12/15

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

Select your answer

assignState()

setState()

changeState()

updateState()

Question 13/15

How do you declare a functional component in React?

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

Select your answer

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

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

By instantiating a new object.

By defining a JavaScript function that returns a React element.

Question 14/15

When should you use React's StrictMode?

Select your answer

To identify potential problems in an application by activating additional checks and warnings.

To restrict the app to use only the 'useState' hook.

To enforce strict variable naming conventions.

To run the app only in development mode.

Question 15/15

How can you pass data from a parent to a child component in React?

Select your answer

By using a custom JavaScript event.

By using the 'import' keyword within the child component.

By calling a method on the child's instance.

By passing props from the parent to the child component.

Your Results

You did not answer any questions correctly.

Your Answers

Question 1/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is JSX in React?

Available answers

A JavaScript library for managing forms.

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

A framework for building REST APIs.

A style sheet language used for describing presentation.

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 2/15

😊 Your answer was correct 🙁 Your answer was incorrect

How do you create a class-based component in React?

class MyComponent extends React.Component {
  render() {
    return <div>Hello World</div>;
  }
}

Available answers

By using the 'class' keyword and extending 'React.Component'.

By creating an HTMLElement instance.

By using the 'function' keyword and returning a string.

By using an anonymous function expression.

To create a class-based component in React, you use the 'class' keyword to define a new class that extends 'React.Component'. This class must include a 'render()' method that returns a React element.

Question 3/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which of these statements about state in React is true?

Available answers

State is the same as props.

State is static and does not update once the component is mounted.

State should be mutated directly for updates.

State is a way to hold dynamic data and can influence the output of a component's render function.

State in React is used to store dynamic data that may change over time and influence the output of a component's render function. Contrary to props, which are passed into a component, state is local to the component and managed entirely within it.

Question 4/15

😊 Your answer was correct 🙁 Your answer was incorrect

How does React update the user interface efficiently?

Available answers

By sending AJAX requests every few seconds to refresh the page.

By using a virtual DOM to track changes and update only the affected parts of the DOM.

By directly manipulating the DOM every time a change occurs.

By using a single HTML file that is reloaded every change.

React efficiently updates the user interface by using a virtual DOM. When changes occur, React creates a virtual DOM and calculates the differences between the new and previous versions. React then updates only the parts of the real DOM that changed, improving performance and reducing unnecessary updates.

Question 5/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you bind functions to the correct context in React class components?

Available answers

By using arrow functions or binding them in the constructor.

By using the 'delay' prop on method calls.

By creating new instances inside render.

By declaring them outside the component scope.

In React class components, you can ensure methods have the correct context using arrow functions (since they don't create a 'this' context) or explicitly binding them using the

bind()

method inside the constructor.

Question 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is a React component?

Available answers

A CSS file that styles the user interface.

A bundle of functions that performs HTTP requests.

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

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

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 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

How do you write comments in JSX?

Available answers

Comments are not allowed in JSX.

For block comments, surround the code with /* comments */.

Use hashtags like #comment.

Use curly braces and an asterisk: {/* Your comment here */}

In JSX, you write comments using curly braces and '/* *'/ syntax. This allows for comments to be embedded within JSX code:

{/* Your comment here */}

. Regular JavaScript comments outside JSX work the same as usual.

Question 8/15

😊 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

Immediately stops executing the component function.

Only works in class components.

Defines the UI to be rendered to the DOM.

Executes a function upon rendering.

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 9/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

setState()

componentDidMount()

render()

getInstance()

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 10/15

😊 Your answer was correct 🙁 Your answer was incorrect

How do you handle events in React?

Available answers

By using the 'bind' attribute in HTML.

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

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

Can React handle asynchronous operations within components?

Available answers

No, React components cannot perform asynchronous operations.

Yes, but only in class components using setState.

Yes, by using lifecycle methods or hooks such as useEffect.

Yes, but only with external libraries, as React does not support it natively.

React can handle asynchronous operations such as API calls and timers within components. You can use lifecycle methods like 'componentDidMount' in class components or 'useEffect' hooks in function components to perform these operations.

Question 12/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

assignState()

setState()

changeState()

updateState()

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 13/15

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

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

By instantiating a new object.

By defining a JavaScript function that returns a React element.

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 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

When should you use React's StrictMode?

Available answers

To identify potential problems in an application by activating additional checks and warnings.

To restrict the app to use only the 'useState' hook.

To enforce strict variable naming conventions.

To run the app only in development mode.

<React.StrictMode>

is used for highlighting potential problems in a React application. Enclosing the application in

<React.StrictMode>

helps developers identify unsafe lifecycles, legacy API usage, and multiple driver side effects.

Question 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you pass data from a parent to a child component in React?

Available answers

By using a custom JavaScript event.

By using the 'import' keyword within the child component.

By calling a method on the child's instance.

By passing props from the parent to the child component.

To pass data from a parent to a child component in React, props are used. You can pass String, Object, Array, and Function in the props.