Top 15+ ES6 Interview Questions and Answers

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ES6 stands for ECMAScript 2015. It was a major update that made JavaScript more powerful and easier to use. Before ES6, the language lacked many features found in modern programming. This update introduced arrow functions, classes, modules, and promises – making code cleaner and more efficient.ES6 was introduced by Brendan Eich and later standardized by ECMA International. Today, it is widely used in web development and is a must-know for roles such as front-end developer or full-stack engineer. If you are preparing for one of these roles, these ES6 interview questions and answers can give you a strong head start.

Fun Fact – Over 98% of websites use JavaScript, and more than 90% of those use ES6 features to support modern functionality.

ES6 Interview Questions for Freshers 

Here are some commonly asked ES6 interview questions and answers to help freshers prepare for JavaScript interview.

1. What is ES6 and why was it introduced?

ES6 stands for ECMAScript 2015. It was introduced to fix limitations in JavaScript. It brought cleaner syntax and modern features like classes, modules, and promises. These changes made the language easier for large applications.

2. What is the difference between var, let, and const in ES6?

var is function-scoped and can be redeclared. let and const are block-scoped. let allows updates, while const does not. With const, you can’t reassign the variable itself, but object properties can still be changed.

3. How are arrow functions different from regular functions in JavaScript?

Arrow functions are shorter and don’t have their own this or arguments. They are best for short functions and callbacks. You can’t use them as constructors or hoist them like regular functions.

4. What are template literals and how are they used in ES6?

Template literals are strings wrapped in backticks (`) instead of quotes. They allow multi-line strings and expression interpolation using ${}. This makes it easier to build dynamic strings without using + for concatenation.

5. What is destructuring in ES6? Give examples for both arrays and objects.

Destructuring lets you unpack values from arrays or objects into variables.

Example (array): const [x, y] = [1, 2]

Example (object): const {name, age} = person

It saves time and makes code cleaner.

6. How does the spread operator work in ES6 and where can you use it?

The spread operator (…) expands arrays or objects.

Example: const arr = […a, …b]

You can use it to copy data, merge arrays, or pass arguments.

ES6 JavaScript Interview Questions for Experienced 

This section covers important ES6 interview questions and answers for experienced professionals.

7. What is the Temporal Dead Zone in ES6?

The Temporal Dead Zone (TDZ) is the time between entering a block and the variable being declared. Accessing a let or const variable before its declaration throws a ReferenceError. It exists to avoid bugs caused by accessing variables too early.

8. How do Promises work in ES6 and what problems do they solve?

Promises help manage asynchronous code. A Promise has three states: pending, fulfilled, and rejected. Instead of using nested callbacks, you chain .then() and .catch() for cleaner logic. This avoids “callback hell” and makes error handling easier.

9. What is the difference between Map and WeakMap in JavaScript?

Map allows keys of any type and keeps strong references. It supports size, iteration, and various methods. 

WeakMap only accepts objects as keys and holds weak references, meaning keys can be garbage collected. WeakMap is not iterable.

10. What are proxies in ES6 and when would you use them?

Proxies let you control how objects behave. You can intercept actions like reading or writing properties. They are useful for validation, logging, or custom access behavior.

Example: hiding internal values or creating fallback responses.

11. What are generator functions and how do they differ from regular functions?

Generator functions use the function* syntax and return an iterator object. You can pause their execution using yield and resume it later. Unlike regular functions, which run from start to finish, generators allow you to manage sequences, lazy evaluation, and complex control flows more efficiently.

ES6 Features Interview Questions

Here are some key ES6 features in JavaScript interview questions to test your understanding of modern syntax and functionality.

12. What are the most important features introduced in ES6?

ES6 added key features like let, const, arrow functions, classes, template literals, destructuring, default and rest parameters, promises, modules, and the spread operator. These changes made JavaScript more modern and easier to write.

13. How do default parameters work in ES6 functions?

Default parameters let you assign fallback values to function arguments. If no value is passed or it’s undefined, the default kicks in.

Example:

function greet(name = ‘Guest’) { return `Hello, ${name}` }  

14. What is the rest parameter in ES6 and how is it different from arguments?

The rest parameter (…args) collects remaining arguments into an array. It is cleaner and supports array methods directly.

Unlike arguments, rest parameters don’t include non-passed parameters and don’t work in arrow functions.

15. How does ES6 support object-oriented programming with classes and inheritance?

ES6 introduced class syntax to define constructors and methods. You can use extends to inherit from a parent class and super() to call the parent constructor. It made OOP feel more structured and closer to other languages.

ES6 Coding Interview Questions

Here are practical ECMAScript interview questions that test your ability to write and understand real ES6 code in JavaScript interviews.

16. Write a function using arrow syntax that adds two numbers.

const add = (a, b) => a + b;

console.log(add(3, 5)); // Output: 8

17. Write an ES6 function that swaps two variables using destructuring.

let x = 10, y = 20;

[x, y] = [y, x];

console.log(x, y); // Output: 20 10

18. Write an example using the spread operator to merge two arrays.

const arr1 = [1, 2, 3];

const arr2 = [4, 5, 6];

const merged = […arr1, …arr2];

console.log(merged); // Output: [1, 2, 3, 4, 5, 6]

19. Create a simple class in ES6 with a constructor and a method.

class Person {

  constructor(name) {

    this.name = name;

  }

  greet() {

    return `Hi, I’m ${this.name}`;

  }

}

const user = new Person(‘Alice’);

console.log(user.greet()); // Output: Hi, I’m Alice

Tips to Prepare for ES6 JavaScript Interview Questions

ES6 is a core part of modern JavaScript interviews and often tests real coding ability. Here are some tips to answer ES6 interview questions. 

• Practice writing code with let, const, arrow functions, and destructuring
• Understand how promises and async code work
• Build small apps using ES6 classes and modules
• Read code on GitHub to see ES6 in action
• Use online tools like JSFiddle or CodePen to test concepts quickly and interactively

Also Read - Top 60+ JavaScript Interview Questions and Answers

Wrapping Up

So, these are the 15+ most asked ES6 interview questions that can help you prepare better. Make sure to practice coding regularly and understand how ES6 works in real projects. It is a must-know for JavaScript roles today.

Looking for ES6 JavaScript roles? Find top tech openings on Hirist today. 

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