ES6 (ECMAScript 2015) interview questions

 1. What is ES6?
ES6 (ECMAScript 2015) is the sixth edition of the ECMAScript standard. It is a major update to JavaScript, introducing new syntax and features to enhance the language.

2. What are the new features introduced in ES6?

Some key features include let and const declarations, arrow functions, classes, destructuring, template literals, spread/rest operators, and promises.

3. What is the difference between let, const, and var?
let and const have block-level scope and do not hoist, while var has function-level scope and hoists. const cannot be reassigned, but let and var can.

4. What are arrow functions, and how do they differ from regular functions?
Arrow functions have a concise syntax and do not bind their own this. They are especially useful for short, non-method functions.

5. Explain the concept of template literals.
Template literals allow embedding expressions inside string literals using ${} syntax. They make string interpolation and multiline strings more convenient.

6. What is destructuring in ES6?
Destructuring is a concise way to extract values from arrays and objects. It simplifies assignment and can be used in function parameters as well.

7. How does the class keyword simplify object-oriented programming in JavaScript?
The class keyword provides a more straightforward syntax for creating constructor functions and managing prototypes, making it easier to work with object-oriented concepts.

8. What is the purpose of the spread operator (...)?
The spread operator is used to unpack elements from arrays or properties from objects. It is handy for creating shallow copies, combining arrays, and passing multiple arguments to functions.

9. What are Promises in JavaScript?
Promises are objects representing the eventual completion or failure of an asynchronous operation. They simplify async code, making it more readable and maintainable.

10. What is the async/await feature in ES6?
async/await is a syntactic sugar for working with Promises. async functions return Promises, and await is used to pause execution until the Promise is resolved.

11. How does ES6 address the callback hell problem?
ES6 introduces Promises and async/await, which provide more readable and manageable ways to handle asynchronous operations, reducing the callback hell problem.

12. Explain the concept of modules in ES6.
ES6 modules allow developers to organize code into separate files, making it more modular and maintainable. Modules have their own scope, and their exports/imports are statically analyzed.

13. What is the purpose of the let keyword in a for...of loop?
The let keyword in a for...of loop creates a block-scoped variable for each iteration, preventing unintended side effects when working with closures and asynchronous code.

14. What is the purpose of the Symbol data type in ES6?
Symbol is a new primitive data type that creates unique values, useful for creating private object properties and avoiding naming collisions.

15. How does ES6 enhance object literals?
ES6 enhances object literals with features like shorthand property names, computed property names, and method definitions, making object creation and manipulation more concise.