20 Arrow Functions Interview Questions and Answers

Arrow functions are a relatively new feature of JavaScript, and as such, interviewers may still be testing your knowledge on them. If you’re applying for a position that involves JavaScript, it’s important to be prepared to answer questions about arrow functions. In this article, we’ll go over some of the most common arrow function questions so you can ace your next interview.

Arrow Functions Interview Questions and Answers

Here are 20 commonly asked Arrow Functions interview questions and answers to prepare you for your interview:

1. What are arrow functions in JavaScript?

Arrow functions are a type of function that is shorthand for a traditional function expression. They are anonymous and can be used in place of a function expression. Arrow functions are often used in callback functions and array methods.

2. Can you give me a real-world example of using an arrow function?

Arrow functions are often used in React applications, for example in the onClick event handler:

onClick={() => this.setState({isOpen: !this.state.isOpen})}

3. What is the difference between normal functions and arrow functions in JavaScript?

Arrow functions are a more concise way to write functions in JavaScript. They do not have their own this keyword, so they can only be used in situations where the this keyword is inherited from the surrounding scope. Additionally, arrow functions do not have their own arguments object, so they cannot be used as arguments to other functions.

4. Do all programming languages support arrow functions? If not, how do they implement functional programming concepts without them?

No, not all programming languages support arrow functions. Some languages that don’t support arrow functions implement functional programming concepts by using higher-order functions. Higher-order functions are functions that take other functions as arguments or return functions as output.

5. What’s the best way to handle anonymous functions with arrow functions in JavaScript?

There are a few different ways to handle anonymous functions with arrow functions in JavaScript. One way is to simply assign the arrow function to a variable, and then call that variable when you want to execute the function. Another way is to use an immediately-invoked arrow function, which will execute the function as soon as it is defined.

6. What does this arrow function do: “() => 1 + 2”? Why would someone write such a thing?

This arrow function returns the value 3. It is equivalent to writing “function() { return 1 + 2; }”. The reason someone might write such a thing is to save space, as the arrow function is much shorter.

7. Is it possible to create nested arrow functions? If yes, then what are those called?

Yes, it is possible to create nested arrow functions. These are called “curried arrow functions.” Curried arrow functions are named after the mathematician Haskell Curry, who developed the concept of currying functions. Currying is a way of breaking down a function into smaller functions, each of which takes one argument.

8. Are there any drawbacks to using arrow functions?

While arrow functions do have some benefits, there are also a few drawbacks to consider. One is that they can be confusing to read if they are not written correctly. Another is that they do not bind to the ‘this’ keyword, so if you need to access ‘this’ within an arrow function, you will need to use a work-around.

9. How can you pass a parameter while calling an arrow function?

When you are defining an arrow function, you can specify the input parameters by enclosing them in parentheses. When you are calling the function, you can pass in the arguments in the same way as you would for any other function.

10. What happens if you don’t use the parentheses while defining an arrow function that accepts one parameter?

If you don’t use parentheses while defining an arrow function that accepts one parameter, then the function will automatically return the value of the parameter.

11. How would you define an arrow function that doesn’t take any parameters at all?

An arrow function that doesn’t take any parameters would look like this: () => {}.

12. In the context of arrow functions, what does the term ‘lexical binding’ mean?

In JavaScript, the term ‘lexical binding’ refers to the way in which the function’s this keyword is bound to the surrounding code. In arrow functions, the this keyword is always bound lexically, which means that it can only be accessed within the function itself and not from any outer scope. This can be useful for ensuring that the this keyword always refers to the same object, no matter where the function is invoked from.

13. Can you explain the advantages of lexical binding for arrow functions?

There are a few advantages that come with lexical binding for arrow functions. First, it makes it easier to read code that uses arrow functions because the this keyword is always bound to the lexical scope. This means that you don’t have to worry about the value of this changing depending on how the function is called. Additionally, lexical binding can help to make your code more concise because you don’t have to write out the function keyword or use the bind method to explicitly bind this to a value.

14. What is currying?

Currying is a technique in functional programming whereby a function is called with fewer arguments than it is expecting, and the function returns a new function that takes the remaining arguments. This can be useful for creating specialized functions, or for creating functions that are easier to compose.

15. What’s the significance of closures when talking about arrow functions?

Closures are a big part of arrow functions – they allow you to access variables from the parent scope inside of the arrow function. This is significant because it means that you can create functions that are more concise and easier to read, while still being able to access all the information you need.

16. Can you explain the differences between ES5, ES2015 (ES6), and ES2016 (ES7) arrow functions?

The main difference between arrow functions and traditional functions is that arrow functions do not have their own this keyword. This means that they can only inherit the this keyword from the parent scope. In addition, arrow functions are always anonymous, which means that they cannot be used as constructors. Finally, arrow functions do not have a prototype property.

17. What is the purpose of default parameters in arrow functions? When should we use them?

Default parameters in arrow functions are used to provide a default value for a parameter in case no value is passed in for that parameter. This can be useful in a number of situations, such as when you want to provide a default value for a parameter that is likely to be omitted by the user.

18. How can you invoke an array method like map or reduce inside an arrow function?

You can invoke an array method like map or reduce inside an arrow function by using the Function.prototype.call method. For example:

“`
const myArray = [1, 2, 3];

const mappedArray = myArray.map(function(item) {
return item * 2;
});

const mappedArray = myArray.map(item => item * 2);
“`

19. What’s the best way to make sure that our code works on several browsers without worrying about compatibility issues related to arrow functions?

The best way to make sure that our code works on several browsers without worrying about compatibility issues related to arrow functions is to use a transpiler. A transpiler is a tool that converts code from one language to another. In this case, it would take our code written in ES6 with arrow functions and convert it into ES5 code, which is compatible with all browsers.

20. What is transpiling?

Transpiling is the process of converting code from one language to another. In the case of arrow functions, this would mean converting code written in ES6 to ES5. This is important because arrow functions are not yet supported by all browsers. By transpiling the code, you can ensure that your code will still run even if the browser does not support arrow functions.