Javascript Functions MCQ - Quiz

Q: What does the `setInterval()` function do in JavaScript?

A. Executes a function once after a specified time interval
B. Executes a function repeatedly at a specified time interval
C. Stops a function from being executed repeatedly
D. None of these

Correct Option: B
Explanation:

The setInterval() function executes a function repeatedly at a specified time interval (in milliseconds).
To stop the function from being executed, you can use the clearInterval() function.
This is useful when you want to perform a certain task at regular intervals, such as updating a value on a webpage or checking for new data from a server. The clearInterval() function is used to stop the function from being executed.
It takes the ID of the interval as an argument, which is returned by the setInterval() function when it is called.

Q: What does the this keyword refer to in the following code?

const user = {
name: 'John',
greet: () => {
console.log('Hello, ' + this.name + '!');
}
}

user.greet();

A. the global object
B. the function itself
C. the object that the function is a property of
D. the object that the function is called on

Correct Option: A
Explanation:

In this case, the greet function is an arrow function, which means that the this keyword is not dynamically bound to the object that the function is called on.
Instead, it refers to the value of this in the surrounding context, which in this case is the global object.

Q: What is a higher-order function in JavaScript?

A. A function that returns another function
B. A function that takes another function as an argument
C. A function that does both of the above
D. none of these

Correct Option: C
Explanation:

A higher-order function is a function that either returns another function or takes another function as an argument, or both.
Higher-order functions are a powerful tool in functional programming because they allow you to create new functions by combining and modifying existing ones.

Q: What does the `isFinite()` function do in JavaScript?

A. Checks if a value is a finite number
B. Checks if a value is infinite
C. Checks if a value is not a number
D. None of these

Correct Option: A
Explanation:

The isFinite() function checks if a value is a finite number.
It returns true if the value is a finite number, and false if it is not.

Q: What is a generator function in JavaScript?

A. A function that returns an iterator
B. A function that yields a value
C. A function that does both of the above
D. None of these

Correct Option: C
Explanation:

A generator function is a function that returns an iterator and can yield a value multiple times.
Generator functions are denoted by the * symbol and can be paused and resumed at any time.
They are often used to create asynchronous code that is easier to read and maintain.

Q: What does the `sort()` function do in JavaScript?

A. Sorts the elements of an array in ascending order
B. Sorts the elements of an array in descending order
C. Sorts the elements of an array in random order
D. None of these

Correct Option: A
Explanation:

The sort() function sorts the elements of an array in ascending order.
By default, it compares the elements as strings.
You can pass a comparison function as an argument to sort the elements in a different way.

Q: What is the result of the following function call in JavaScript?

add(10, 5);

function add(x, y) {
return x + y;
}

A. 15
B. '105'
C. undefined
D. TypeError

Correct Option: A
Explanation:

In this case, the add function is defined before it is called, so the function call is successful and returns the sum of the two numbers, 15.

Q: What is a callback function in JavaScript?

A. A function that is executed after a certain event occurs
B. A function that is passed as an argument to another function
C. A function that is executed immediately
D. None of these

Correct Option: B
Explanation:

A callback function is a function that is passed as an argument to another function.
It is called (or "executed") when the event that it was passed to occurs.
Callback functions are often used to execute a certain task after an asynchronous operation has completed.

Q: What is a closure in JavaScript?

A. A function that is defined inside another function
B. A function that has access to the outer function's variables
C. A function that is bound to an object
D. None of these

Correct Option: B
Explanation:

A closure is a function that has access to the outer function's variables even after the outer function has returned.
Closures are created when a function is defined inside another function and the inner function has access to the outer function's variables.
Closures are often used to create private variables and to preserve state in callback functions.

Q: What does the this keyword refer to in the following code?

function greet() {
console.log('Hello, ' + this.name + '!');
}

A. the global object
B. the function itself
C. the object that the function is a property of
D. the object that the function is called on

Correct Option: C
Explanation:

In this case, the greet function is a property of an object, and the this keyword refers to that object.

Javascript Functions MCQ - Quiz

What does the `setInterval()` function do in JavaScript?

What does the this keyword refer to in the following code?
const user = { name: 'John', greet: () => { console.log('Hello, ' + this.name + '!'); } } user.greet();

What is a higher-order function in JavaScript?

What does the `isFinite()` function do in JavaScript?

What is a generator function in JavaScript?

What does the `sort()` function do in JavaScript?

What is the result of the following function call in JavaScript?
add(10, 5); function add(x, y) { return x + y; }

What is a callback function in JavaScript?

What is a closure in JavaScript?

What does the this keyword refer to in the following code?
function greet() { console.log('Hello, ' + this.name + '!'); }

Javascript Functions MCQ - Quiz

What does the setInterval() function do in JavaScript?

What does the this keyword refer to in the following code? const user = { name: 'John', greet: () => { console.log('Hello, ' + this.name + '!'); } } user.greet();

What is a higher-order function in JavaScript?

What does the isFinite() function do in JavaScript?

What is a generator function in JavaScript?

What does the sort() function do in JavaScript?

What is the result of the following function call in JavaScript? add(10, 5); function add(x, y) { return x + y; }

What is a callback function in JavaScript?

What is a closure in JavaScript?

What does the this keyword refer to in the following code? function greet() { console.log('Hello, ' + this.name + '!'); }

What does the `setInterval()` function do in JavaScript?

What does the this keyword refer to in the following code?
const user = { name: 'John', greet: () => { console.log('Hello, ' + this.name + '!'); } } user.greet();

What does the `isFinite()` function do in JavaScript?

What does the `sort()` function do in JavaScript?

What is the result of the following function call in JavaScript?
add(10, 5); function add(x, y) { return x + y; }

What does the this keyword refer to in the following code?
function greet() { console.log('Hello, ' + this.name + '!'); }