1. What is JavaScript?

JavaScript is a high-level, interpreted programming language used to build interactive web applications. It runs inside browsers and can also run on servers using Node.js.

• Client-side scripting language
• Supports asynchronous programming
• Used in frontend and backend development
• Supports object-oriented and functional programming

2. Difference Between var, let, and const

JavaScript provides three ways to declare variables: var, let, and const.

3. What is Hoisting in JavaScript?

Hoisting is JavaScript's default behavior of moving declarations to the top of their scope before execution.

console.log(name);

var name = "TechQA";

        

Explore More JavaScript Interview Questions

Practice advanced JavaScript concepts including closures, promises, async/await, DOM, and ES6 features.

4. What is a Closure in JavaScript?

A closure is a function that remembers variables from its outer scope even after the outer function has executed.

function outer() {
  let count = 0;

  return function inner() {
    count++;
    return count;
  };
}

        

5. What is the Difference Between == and === ?

The == operator compares values after type conversion, while === compares both value and data type without conversion.

5 == "5"   // true

5 === "5"  // false

        

6. What are Promises in JavaScript?

Promises are used to handle asynchronous operations in JavaScript.

• Pending
• Resolved
• Rejected

fetch('/api/users')
  .then(res => res.json())
  .then(data => console.log(data));

        

Learn Advanced JavaScript Concepts

Improve your frontend interview preparation with advanced JavaScript tutorials and coding examples.

Final Thoughts

JavaScript interviews in 2026 focus heavily on asynchronous programming, closures, ES6 features, DOM manipulation, and performance optimization.

Build real-world projects, practice coding regularly, and strengthen your JavaScript fundamentals to become a successful web developer.