React Basics Quiz

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Question 1/15

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

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Question 2/15

What is the significance of 'props' in React?

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Question 3/15

What is the purpose of keys in React lists?

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Question 4/15

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

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Question 5/15

What is JSX in React?

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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>;
  }
}

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Question 7/15

How do you declare a functional component in React?
function MyComponent() {
  return <div>Hello World</div>;
}

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Question 8/15

Which statement about 'useState' hook is true?

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Question 9/15

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

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Question 10/15

How do you handle events in React?

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Question 11/15

What does the 'return' statement do in a React component?
function Greeting() {
  return <h1>Hello, world!</h1>;
}

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Question 12/15

What is the difference between state and props?

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Question 13/15

What is the purpose of componentDidMount lifecycle method?

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Question 14/15

What is a React component?

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Question 15/15

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

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Your Answers

Question 1/15
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Which method should be overridden to return a React element from a class component?

Available answers

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
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What is the significance of 'props' in React?

Available answers

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
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What is the purpose of keys in React lists?

Available answers

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

Available answers

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
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What is JSX in React?

Available answers

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
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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

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
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How do you declare a functional component in React?
function MyComponent() {
  return <div>Hello World</div>;
}

Available answers

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
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Which statement about 'useState' hook is true?

Available answers

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

Available answers

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
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How do you handle events in React?

Available answers

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
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What does the 'return' statement do in a React component?
function Greeting() {
  return <h1>Hello, world!</h1>;
}

Available answers

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
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What is the difference between state and props?

Available answers

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
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What is the purpose of componentDidMount lifecycle method?

Available answers

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
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What is a React component?

Available answers

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

Available answers

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.