Introduction
If you're nervous about technical screens, focused practice on ES6 interview questions moves you from guesswork to precision. ES6 interview questions are the backbone of many front-end and full-stack interviews; mastering them shows you can write modern, maintainable JavaScript and reason about common pitfalls. This guide gives clear answers, practical examples, and preparation tips tied to real search intent so you can target the exact topics hiring managers ask about.
For further reading and practice, see collections from Final Round AI, Verve Copilot’s ES6 list, the Tech Interview Handbook, Stackademic’s study guide, GeeksforGeeks, DevSkiller, and InterviewBit for problem drills and expanded explanations.
Takeaway: Focus on the ES6 interview questions that show your ability to write clear, bug-resistant code under time pressure.
Core ES6 Features You Will Be Asked About
ES6 introduced syntax and primitives like let/const, arrow functions, template literals, destructuring, default params, classes, modules, and promises. These features modernize JavaScript and appear repeatedly in ES6 interview questions because they change common patterns and debugging behavior. Include short code examples in your study notes: compare var vs let, show arrow-function this behavior, and rewrite a callback with async/await. Takeaway: Solid examples plus failure modes are the fastest path to interview-ready answers.
Technical Fundamentals
Q: What are the main features introduced in ES6?
A: Block-scoped variables (let/const), arrow functions, classes, template literals, destructuring, default parameters, modules, promises, Map/Set, and generators.
Q: How do template literals work in ES6?
A: Template literals use backticks for string interpolation and multi-line strings: \`Hello ${name}\` and preserve newlines.
Q: What is destructuring assignment in JavaScript?
A: Destructuring extracts values from arrays or properties from objects into variables: const {x, y} = point.
Q: What are default parameters in ES6?
A: Functions can set defaults directly: function f(a = 1, b = 2) {} which avoids checks inside the function.
Q: What new collections did ES6 add?
A: Map, Set, WeakMap, and WeakSet provide keyed collections and improved semantics for unique values and memory management.
Q: Why are arrow functions significant?
A: Arrow functions provide concise syntax and lexical this binding, making them safer for callbacks and functional patterns.
Variable Scoping and Declaration: What Interviewers Expect
let and const offer block scoping and predictable redeclaration rules; var remains function-scoped and hoisted. Expect questions that test hoisting, temporal dead zone, and when to prefer const for intent and immutability. Demonstrate examples where let prevents bugs that var would introduce. Takeaway: Explain behavior and prefer const-by-default with let for reassignable bindings.
Variable Scoping
Q: Explain the difference between var, let, and const in JavaScript.
A: var is function-scoped and hoisted; let/const are block-scoped; const forbids reassigning the binding.
Q: What is the temporal dead zone (TDZ)?
A: The TDZ is the period between entering a scope and a let/const binding's initialization; accessing it throws a ReferenceError.
Q: What happens if I redeclare a let variable?
A: Redeclaring a let in the same scope throws a SyntaxError; in different blocks it's allowed.
Q: How does hoisting relate to ES6 declarations?
A: Declarations are hoisted, but let/const are uninitialized during the TDZ, unlike var which is initialized to undefined.
Functions and Arrow Syntax: Concise, Lexical, and Safe
Arrow functions change how this is bound and cannot be used as constructors; rest/spread and default parameters simplify API design. Interviewers will test when lexical this is beneficial and when function expressions are still required. Practice converting callbacks to arrow functions and using rest parameters in utility functions. Takeaway: Explain both syntax and semantics with small examples.
Functions and Arrow Syntax
Q: How do you write an arrow function in ES6?
A: Use const f = (x) => x * 2; omit parentheses for single params and braces for single-expression returns.
Q: What is the ‘this’ binding in arrow functions?
A: Arrow functions use lexical this from the enclosing scope; they do not create their own this value.
Q: Can arrow functions be used as constructors?
A: No. Arrow functions have no prototype and cannot be used with new; they throw when used as constructors.
Q: What are rest parameters and how do they differ from arguments?
A: Rest (...args) gathers remaining args into an array; arguments is array-like and not usable in arrow functions.
Q: How to use default parameters in ES6 functions?
A: Set defaults in signature: function f(a=1,b=2){}; defaults evaluate at call time.
Object-Oriented Programming and Classes: Modern Patterns
ES6 classes provide syntactic sugar over prototype-based inheritance, with clearer subclassing via extends and super. Expect questions on prototype chain differences, private fields, and how class methods are not automatically bound. Show a subclass example using super and explain when to use prototypes directly. Takeaway: Use class syntax to communicate intent, but understand prototypes under the hood.
Classes and OOP
Q: How to create a class in ES6?
A: Use class Person { constructor(name){ this.name = name } greet(){ return this.name } }.
Q: What is the purpose of the super keyword in ES6 classes?
A: super calls the parent class constructor or methods and is required before using this in subclasses.
Q: Can you use private fields in ES6 classes?
A: Modern JS supports private fields with #name; older patterns used closures or Symbols for privacy.
Q: How do ES6 classes differ from ES5 constructor functions?
A: Classes provide clearer syntax and semantics but are still prototype-based under the hood; class methods are non-enumerable.
Asynchronous JavaScript and Promises: Scenario-Based Answers Win
Promises and async/await replace deeply nested callbacks and are common in ES6 interview questions because they reflect real-world async patterns. Be prepared to explain Promise states, chaining, error propagation, and converting callback APIs to promise-based ones. Include an async/await example showing try/catch for errors. Takeaway: Show both promise chaining and async/await, and explain common race/concurrency patterns.
Async and Promises
Q: What is a Promise in ES6?
A: A Promise is an object representing asynchronous completion or failure, with then and catch for chaining.
Q: How to write a function that returns a promise?
A: function fetchData(){ return new Promise((resolve,reject)=>{ / async work / }) }.
Q: What is the difference between synchronous and asynchronous programming?
A: Synchronous runs sequentially; asynchronous defers work (e.g., I/O) allowing other code to run while waiting.
Q: How does async/await work with ES6 promises?
A: async marks a function; await pauses execution until a promise resolves, returning the resolved value or throwing on rejection.
Modules and Code Organization: What to Know for Scalable Apps
ES6 modules (import/export) provide static structure and clear dependency graphs; named vs default exports change how consumers import. Be ready to contrast static imports with dynamic import() for code-splitting and how module scope prevents global leakage. Takeaway: Show how modules improve maintainability and mention dynamic import for lazy-loading.
Modules and Code Organization
Q: How do ES6 modules work?
A: Modules export bindings via export and import them with import; they run once and create live bindings.
Q: How to export and import modules in JavaScript?
A: export function f(){} and import {f} from './mod'; default exports use export default.
Q: What is the difference between named and default exports?
A: Named exports require curly braces and allow multiple exports; default exports export a single value without braces.
Iterators, Generators, and New Data Structures: Advanced Topics
Iterators and generators enable custom lazy sequences and control flow; for..of consumes iterables while for..in iterates keys. Map/Set and WeakMap/WeakSet have different performance and memory semantics. Interviewers for senior roles expect you to explain use-cases and pitfalls. Takeaway: Practice generator examples and explain when iterators improve performance or readability.
Iterators and Generators
Q: What is the difference between for..of and for..in loops?
A: for..in iterates enumerable property names; for..of iterates values of iterables like arrays or Maps.
Q: What are generators in ES6?
A: Generators (function*) yield values and can pause/resume execution, useful for lazy sequences and async patterns.
Common Interview Preparation Strategies for ES6 Interview Questions
Target practice on high-frequency ES6 interview questions, build concise sample snippets, and run mock interviews that emphasize explanation and edge cases. Combine reading resources with timed coding and explanation drills; measure progress by the ability to articulate trade-offs. Takeaway: Prioritize clear examples, failure modes, and speed of explanation.
Preparation Best Practices
Q: How to prepare for an ES6 technical interview?
A: Practice concise examples, explain trade-offs, use timed drills, and review common pitfalls like TDZ and lexical this.
Q: What are the most common mistakes in ES6 interviews?
A: Confusing var/let/const, misusing this in callbacks, and not handling promise rejections.
How Verve AI Interview Copilot Can Help You With This
Verve AI Interview Copilot provides real-time feedback on your ES6 interview questions answers, helping you structure responses, clarify trade-offs, and rehearse edge cases. It simulates interviewer follow-ups and highlights missing details like TDZ, promise error paths, or module semantics. Use it to practice timed answers and get adaptive prompts that push you to explain reasoning clearly. Try Verve AI Interview Copilot for targeted drills, review recorded answers, and refine technical explanations with instant actionable tips from Verve AI Interview Copilot — all designed to reduce interview stress and boost clarity with Verve AI Interview Copilot.
What Are the Most Common Questions About This Topic
Q: Can Verve AI help with behavioral interviews?
A: Yes. It applies STAR and CAR frameworks to guide real-time answers.
Q: How long should I practice each ES6 topic?
A: Focus 30–60 minutes per topic, then review weaknesses.
Q: Are code examples necessary in answers?
A: Yes. Short, correct snippets prove competence quickly.
Q: Will mock interviews improve my timing?
A: Yes. Simulated rounds build pacing and clarity.
Q: Can I practice async/await scenarios with tools?
A: Yes. Run small services or mocks to simulate async flows.
Conclusion
Mastering ES6 interview questions gives you clarity, structure, and confidence in technical screens—practice concise explanations, show example code, and cover failure modes. Focus on let/const behavior, lexical this, promises/async, modules, and classes, and rehearse answers under time pressure. Try Verve AI Interview Copilot to feel confident and prepared for every interview.
