Search Tutorials


ReactJS MCQ Questions and Answers | JavaInUse

ReactJS MCQ Questions and Answers

Q. What is ReactJS?

A. A programming language
B. A front-end JavaScript library for building user interfaces
C. A back-end framework
D. A mobile app development platform

Q. What is a React component?

A. A reusable UI element
B. A function that returns HTML
C. A JavaScript class
All of the above

Q. How do you define a React component using a function?

A. function MyComponent() { return
Hello
}
B. const MyComponent = () => { return
Hello
}
C. class MyComponent { render() { return
Hello
} }
D. None of the above

Q. What is JSX?

A. A markup language
B. A template engine
C. A syntax extension for JavaScript
D. A styling language for React

Q. How do you render a React component to the DOM?

A. Using the render() method
B. With the ReactDOM.render() function
C. By calling the component function
D. Using the React.createElement() function

Q. What is the purpose of props in React?

A. To pass data from a parent component to a child component
B. To manage the state of a component
C. To handle user events
D. To style a component

Q. How can you conditionally render a component in React?

A. Using if-else statements
B. With the switch statement
C. By using the ternary operator
All of the above

Q. What is the purpose of the state in a React component?

A. To store and manage data that can change over time
B. To handle user interactions
C. To pass data between components
D. To control the rendering of a component

Q. How do you update the state in a functional component?

A. By directly modifying the state object
B. Using the setState() method
C. With the useState() hook
D. By passing a new state object as a prop





Q. What is the difference between state and props in React?

A. State is local to a component, while props are passed from a parent component.
B. Props are read-only, while state can be modified.
C. State is used for dynamic data, while props are used for static data.
All of the above

Q. What is the Virtual DOM in React?

A. A lightweight representation of the actual DOM
B. A tool for optimizing performance
C. A way to render components on the server
All of the above

Q. How do you handle events in React?

A. By using HTML event handlers
B. With event listeners
C. Through synthetic events
D. By using callback functions

Q. What is the purpose of the useEffect hook in React?

A. To perform side effects in functional components
B. To optimize performance
C. To manage the component lifecycle
All of the above

Q. What is the difference between React and React Native?

A. React is for web development, while React Native is for mobile development.
B. React uses JavaScript, while React Native uses native code.
C. React Native has a smaller community and less documentation.
All of the above

Q. How do you create a React app using Create React App?

A. By running the create-react-app command in the terminal
B. With a graphical user interface tool
C. By writing a configuration file
D. Using a code generator

Q. Which of the following correctly defines a functional component in React?

A. 
const MyComponent = function() {
  return <div>Hello, World!</div>;
};
B. 
class MyComponent extends React.Component {
  render() {
    return <div>Hello, World!</div>;
  }
}
C. 
function MyComponent() {
  const message = "Hello, World!";
  return <div>{message}</div>;
}
D. 
const MyComponent = () => {
  return <div>Hello, World!</div>;
};

Q. What will be rendered on the webpage when the following code is executed?

const name = "John";
ReactDOM.render(<h1>Hello, {name}!</h1>, document.getElementById('root'));
A. 
Hello, John!
B. 
<h1>Hello, {name}!</h1>
C. 
Hello, {name}!
D. 
Error: Invalid JSX syntax

Q. Which lifecycle method is called before a component is mounted and rendered for the first time?

A. 
componentDidMount()
B. 
componentWillMount()
C. 
componentDidUpdate()
D. 
componentWillUpdate()

Q. How can you conditionally render a component based on a boolean value?

A. 
function MyComponent() {
  const isVisible = true;
  return (
    <div>
      {isVisible && <ChildComponent />}
    </div>
  );
}
B. 
function MyComponent() {
  const isVisible = true;
  if (isVisible) {
    return <ChildComponent />;
  } else {
    return null;
  }
}
C. 
function MyComponent() {
  const isVisible = false;
  return <ChildComponent isVisible={isVisible} />;
}
D. 
function MyComponent() {
  const isVisible = true;
  return <ChildComponent visible={isVisible} />;
}

Q. What will be the output of the following code snippet?

const person = { name: "Alice", age: 30 };
const { name, age } = person;

console.log(name);
console.log(age);
A. 
Alice
30
B. 
undefined
undefined
C. 
Error: Invalid syntax
D. 
null
null

Q. Which of the following is the correct way to define a class component in React?

A. 
function MyComponent() {
  // ...
}
B. 
const MyComponent = () => {
  // ...
};
C. 
class MyComponent {
  // ...
}
D. 
class MyComponent extends React.Component {
  // ...
}

Q. What will be the output of the following code snippet?

const items = [1, 2, 3, 4, 5];
const doubledItems = items.map(item => item * 2);

console.log(doubledItems);
A. 
[2, 4, 6, 8, 10]
B. 
[1, 4, 9, 16, 25]
C. 
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
D. 
[2, 4, 6, 8]

Q. Which lifecycle method is called after a component is updated and re-rendered?

A. 
componentDidMount()
B. 
componentDidUpdate()
C. 
componentWillMount()
D. 
componentWillUpdate()

Q. How can you pass data from a parent component to a child component?

A. 
function ParentComponent() {
  const data = "Hello";
  return <ChildComponent data={data} />;
}
B. 
function ParentComponent() {
  return <ChildComponent data="Hello" />;
}
C. 
function ParentComponent() {
  const data = "Hello";
  return <ChildComponent>{data}</ChildComponent>;
}
D. 
function ParentComponent() {
  const data = "Hello";
  return <ChildComponent getData={data} />;
}

Q. What will be the output of the following code snippet?

const [count, setCount] = React.useState(0);

const handleClick = () => {
  setCount(count + 1);
};

console.log(count);

return (
  <div>
    <button onClick={handleClick}>Increment</button>
  </div>
);
A. 
0
B. 
1
C. 
Error: Invalid syntax
D. 
undefined

Popular Posts





See Also