JavaScript and React Quiz

What will be logged? console.log(typeof null);

• "null"

• "undefined"

• "object"

• "string"

What is the primary purpose of useState in React?

• To create static variables

• To manage state in functional components

• To modify the DOM directly

• To fetch data from APIs

Which HTTP method is commonly used for updating existing data in REST APIs?

• GET

• POST

• PUT

• DELETE

What does fetch() return in JavaScript?

• A resolved value

• A callback function

• A Promise

• An XML object

How do you create a class in JavaScript?

• function MyClass() {}

• class MyClass {}

• new class MyClass {}

• MyClass() => {}

Which of these is a pure function?

• A function that modifies global variables

• A function that always returns the same output for the same input

• A function that depends on Math.random()

• A function that performs AJAX requests

What is the default return value of a JavaScript function if no return statement is provided?

• null

• undefined

• 0

• ""

What is the output of the following code? console.log([..."hello"]);

• "hello"

• ["hello"]

• ['h', 'e', 'l', 'l', 'o']

• SyntaxError

Which of the following is NOT a lifecycle method in React?

• componentDidMount

• componentWillUnmount

• shouldComponentUpdate

• onComponentUpdate

What does the following JavaScript code return? console.log(Promise.resolve(5).then(x => x * 2));

• 5

• 10

• Promise { }

• undefined