JavaScript Functions Quiz - Multiple Choice Questions (MCQ)

Welcome to the JavaScript quiz on functions. This quiz will test your knowledge of JavaScript functions, from basic syntax to more advanced concepts. Each question is accompanied by four options, and explanations are provided for each correct answer to enhance your comprehension. 

Let's dive into the world of JavaScript functions and put your skills to the test!

1. How do you define a function in JavaScript? 

a) 

function myFunction() {} 

b) 

let myFunction = function() {};

c) 

const myFunction = () => {};

d) All of the above 

Answer: 

d) All of the above 

Explanation: 

All three options are valid ways to define functions in JavaScript. Option a) is the traditional function declaration, b) is a function expression, and c) is an arrow function (introduced in ES6).

2. What keyword is used to return a value from a JavaScript function? 

a) value 

b) result 

c) return 

d) output 

Answer: 

c) return 

Explanation: 

The return keyword is used to send a value back from the function to the caller. When the return statement is encountered, the function's execution stops, and the value following the return is returned as the result of the function.

3. How do you call a JavaScript function named myFunction? 

a) call myFunction(); 

b) run myFunction(); 

c) myFunction(); 

d) execute myFunction(); 

Answer: 

c) myFunction(); 

Explanation: 

To call a function in JavaScript, you simply use the function's name followed by parentheses ().

4. What is a callback function in JavaScript? 

a) A function that performs asynchronous tasks. 

b) A function that is called at the end of the program's execution. 

c) A function that is passed as an argument to another function and is executed inside that function. 

d) A function that is used for error handling. 

Answer: 

c) A function that is passed as an argument to another function and is executed inside that function.

Explanation: 

A callback function is a function that is passed as an argument to another function and is executed inside that function. It allows for better control of the flow of asynchronous code in JavaScript.

5. What is a "recursive" function in JavaScript? 

a) A function that includes a loop. 

b) A function that calls itself within its own body. 

c) A function that takes multiple arguments. 

d) A function that executes a callback function. 

Answer: 

b) A function that calls itself within its own body. 

Explanation: 

A recursive function is a function that calls itself during its execution, either directly or indirectly, to solve a problem or perform a repetitive task.

6. What is a "closure" in JavaScript? 

a) A function that is stored as a property of an object. 

b) A function that can be accessed globally from any part of the code. 

c) A function that is defined inside another function and has access to its outer function's variables. 

d) A function that takes an unlimited number of arguments. 

Answer: 

c) A function that is defined inside another function and has access to its outer function's variables.

Explanation: 

A closure is a function that retains access to variables from its containing (enclosing) function's scope, even after the outer function has finished executing.

7. Which method can be used to execute a function after a specified time interval? 

a) executeAfterTime() 

b) setInterval() 

c) executeEvery() 

d) setTimeout() 

Answer: 

d) setTimeout() 

Explanation: 

The setTimeout() method is used to execute a function after a specified delay (time interval) in milliseconds.

8. How can you immediately invoke an anonymous function in JavaScript? 

a) function() { }(); 

b) function { } (); 

c) function { } (); 

d) (function() { })(); 

Answer: 

d) (function() { })(); 

Explanation: 

To immediately invoke an anonymous function, enclose the function declaration in parentheses and add () at the end to call it.

9. What will be the output of the following code?

function greet() {
  console.log("Hello!");
}

var sayHello = greet;
sayHello();

a) Hello! 

b) sayHello 

c) function greet() { console.log("Hello!"); } 

d) undefined 

Answer: 

a) Hello! 

Explanation: 

The variable sayHello is assigned the value of the greet function. When sayHello() is called, it executes the greet function and logs "Hello!" to the console.

10. How do arrow functions differ from regular functions in ES6? 

a) Arrow functions have shorter syntax than regular functions. 

b) Arrow functions do not have their own this value. 

c) Arrow functions cannot be used as methods in objects. 

d) All of the above 

Answer: 

d) All of the above 

Explanation: 

Arrow functions in ES6 have shorter syntax, do not have their own this value (they inherit it from the surrounding scope), and cannot be used as constructors or methods in objects.

Conclusion

Congratulations on completing the JavaScript Functions Quiz! Functions are the building blocks of JavaScript programming, allowing you to write modular and maintainable code. A solid understanding of functions is crucial for mastering JavaScript development. Continue practicing and exploring real-world applications to sharpen your skills further. Happy coding!