Advanced Functions Quiz
Test Yourself !
This quiz builds on the basic functions quiz.
It focuses on this, call(), apply(), bind(), closures, and function references.
If you need a refresher, try the basic quiz first:
Question 1
What does person.getName() return?
const person = {
name: "John",
getName: function() {
return this.name;
}
};
person.getName();
- A. "John"
- B. undefined
- C. "person"
Question 2
What is the value of this when calling getName() like this?
const getName = person.getName;
getName();
- A. It is still the person object
- B. It depends on how the function is called
- C. It is always undefined
Question 3
Which line correctly calls getName with person as this?
const person = { name: "John" };
function getName() { return this.name; }
- A. getName(person)
- B. getName.call(person)
- C. getName.apply = person
Question 4
What is the main difference between call() and apply()?
- A. call() returns a value, apply() does not
- B. call() takes arguments as a list, apply() takes arguments as an array
- C. apply() is faster than call()
Question 5
What does this code return?
function add(a, b) {
return a + b;
}
add.apply(null, [4, 5]);
- A. 9
- B. [4, 5]
- C. null
Question 6
What does bind() do?
- A. Calls a function immediately
- B. Creates a new function with a fixed this value
- C. Converts a function into an arrow function
Question 7
What is stored in getJohn?
function greet() {
return "Hello " + this.name;
}
const person = { name: "John" };
const getJohn = greet.bind(person);
- A. The string "Hello John"
- B. A new function
- C. The person object
Question 8
What does this code return on the second call?
function counter() {
let count = 0;
return function() {
count++;
return count;
};
}
const c = counter();
c();
c();
- A. 1
- B. 2
- C. 0
Question 9
Which statement best describes a closure?
- A. A function that runs immediately
- B. A function that remembers variables from its outer scope
- C. A function that always returns an object
Question 10
What is the difference between passing a function and calling a function?
function sayHello() { return "Hello"; }
function run(fn) { return fn(); }
run(sayHello);
- A. sayHello is passed, sayHello() is called
- B. sayHello() is passed, sayHello is called
- C. There is no difference
Question 11
What is an IIFE used for?
- A. To delay code execution
- B. To create a private scope
- C. To repeat code automatically
Answers
Question 1
Answer: A
Explanation: In an object method, this refers to the owner object.
Question 2
Answer: B
Explanation: When the method is called as a plain function, this is not the object anymore.
Question 3
Answer: B.
Explanation: call() calls the function with a chosen this value.
Question 4
Answer: B.
Explanation: Both set this, but they pass arguments differently.
Question 5
Answer: A.
Explanation: The array values become the function arguments.
Question 6
Answer: B.
Explanation: bind() returns a new function you can call later.
Question 7
Answer: B.
Explanation: bind() does not call the function, it returns a new function.
Question 8
Answer: B.
Explanation: The inner function remembers count (closure).
Question 9
Answer: B.
Explanation: Closures allow functions to remember scope even after the outer function finishes.
Question 10
Answer: A.
Explanation: sayHello is a function reference. sayHello() executes the function.
Question 11
Answer: B.
Explanation: IIFEs were commonly used to avoid global variables.
Quiz Result
If you answered most questions correctly, you understand advanced function concepts.
If not, review the advanced chapters and try again.
