Top JavaScript Interview Questions with Simple Answers (Beginner to Intermediate)
I am a Computer Science graduate learning backend development with Node.js. I enjoy writing beginner-friendly articles and sharing what I learn along my journey. Currently focused on JavaScript, Node.js, and building real-world projects.
JavaScript interview questions are not about writing complex code —
They are about clarity in fundamentals.
This blog covers the most frequently asked JavaScript interview questions, explained in simple language with examples.
🔹 Beginner Level JavaScript Interview Questions
1️⃣ What is JavaScript?
Answer:
JavaScript is a programming language used to make web pages interactive.
It runs in the browser and can also run on the server using Node.js.
2️⃣ Is JavaScript interpreted or compiled?
Answer:
JavaScript is interpreted, but modern browsers use Just-In-Time (JIT) compilation to make it faster.
3️⃣ What are the data types in JavaScript?
Answer:
Primitive:
String
Number
Boolean
Undefined
Null
Symbol
BigInt
Non-Primitive:
Object
Array
Function
4️⃣ Difference between == and ===?
Answer:
==→ compares value only===→ compares value and type
5 == "5"; // true
5 === "5"; // false
5️⃣ What is NaN?
Answer:NaN stands for Not a Number.
It represents an invalid number operation.
Number("abc"); // NaN
🔹 Variable & Scope Questions
6️⃣ Difference between var, let, and const?
Answer:
var→ function scopedlet→ block scopedconst→ block scoped & cannot be reassigned
👉 Best practice: Use const by default.
7️⃣ What is the scope in JavaScript?
Answer:
Scope defines where a variable can be accessed.
Types:
Global Scope
Function Scope
Block Scope
8️⃣ What is hoisting?
Answer:
Hoisting is JavaScript’s behavior of moving declarations to the top before execution.
console.log(a);
var a = 10; // undefined
9️⃣ What is Temporal Dead Zone (TDZ)?
Answer:
TDZ is the time between variable creation and initialization where let and const cannot be accessed.
🔹 Functions & Execution
🔟 What is a function?
Answer:
A function is a block of reusable code that performs a specific task.
function greet() {
console.log("Hello");
}
1️⃣1️⃣ What is an arrow function?
Answer:
Arrow functions are a shorter syntax and do not have their own this.
const add = (a, b) => a + b;
1️⃣2️⃣ Difference between normal function and arrow function?
| Feature | Normal | Arrow |
this | Own | Lexical |
arguments | Available | Not available |
| Constructor | Yes | No |
🔹 Objects & Arrays
1️⃣3️⃣ What is an object?
Answer:
An object stores data in key-value pairs.
const user = { name: "Tushar", age: 22 };
1️⃣4️⃣ Difference between array and object?
Answer:
Array → ordered collection
Object → unordered key-value pairs
1️⃣5️⃣ What is destructuring?
Answer:
Destructuring extracts values from arrays or objects.
const { name } = user;
🔹 Asynchronous JavaScript
1️⃣6️⃣ What is asynchronous JavaScript?
Answer:
Async JavaScript allows code to run without blocking execution.
Example:
setTimeout
API calls
1️⃣7️⃣ What is a callback?
Answer:
A callback is a function passed as an argument to another function.
1️⃣8️⃣ What is a Promise?
Answer:
A Promise represents a value that will be available now, later, or never.
States:
Pending
Fulfilled
Rejected
1️⃣9️⃣ What is async/await?
Answer:async/await makes asynchronous code look synchronous and easier to read.
🔹 DOM & Browser
2️⃣0️⃣ What is DOM?
Answer:
DOM (Document Object Model) represents the HTML structure as objects so JavaScript can manipulate it.
2️⃣1️⃣ How do you select elements in JavaScript?
Answer:
document.getElementById("id");
document.querySelector(".class");
🔹 Common Tricky Questions
2️⃣2️⃣ Difference between null and undefined?
Answer:
undefined→ variable declared but not assignednull→ intentional empty value
2️⃣3️⃣ What is closure?
Answer:
A closure is a function that remembers variables from its outer scope.
2️⃣4️⃣ What is event bubbling?
Answer:
Event bubbling means events propagate from child to parent.
🔹 Final Interview Tips 🚀
✔ Understand concepts, don’t memorise
✔ Practice small programs
✔ Explain answers clearly
✔ Use examples while answering
🔹 Final Words
JavaScript interviews focus on basics + clarity.
If your fundamentals are strong, no interviewer can stop you
🙌 Thanks for Reading!
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