ES6 Interview Questions and Answers for internship

1. What is ES6 (ECMAScript 2015)?

   • Answer: ES6, also known as ECMAScript 2015, is a major update to the JavaScript language that introduced many new features to improve code readability, maintainability, and performance. These features include arrow functions, classes, modules, promises, and more.

2. Explain arrow functions. What are their advantages and disadvantages?

   • Answer: Arrow functions provide a shorter syntax for writing functions. They lexically bind `this`, simplifying handling of `this` within functions. Advantages include concise syntax and lexical `this` binding. Disadvantages include not having their own `this`, `arguments` object, or `new.target`.

3. What are let and const? How do they differ from var?

   • Answer: `let` and `const` are block-scoped variables, meaning their scope is limited to the block of code (e.g., within an `if` statement or loop) they are defined in. `var` is function-scoped. `const` declares a constant value, which cannot be reassigned after its initial declaration. `let` declares a variable whose value can be changed.

4. Explain template literals.

   • Answer: Template literals (backticks ``) allow embedding expressions directly within strings, using `${expression}`. They also support multiline strings without the need for escape characters.

5. What are destructuring assignments? Give examples.

   • Answer: Destructuring allows extracting values from objects and arrays into distinct variables. Example: `const { name, age } = { name: 'John', age: 30 };` extracts `name` and `age` from the object.

6. Explain the spread syntax (...).

   • Answer: The spread syntax expands iterable objects (arrays, strings, maps, sets) into individual elements. It's used for copying arrays, merging objects, and passing multiple arguments to functions.

7. What are rest parameters?

   • Answer: Rest parameters allow a function to accept an indefinite number of arguments as an array. Example: `function sum(...numbers) { ... }`.

8. Explain classes in ES6.

   • Answer: ES6 classes provide a syntactic sugar over prototype-based inheritance. They offer a cleaner way to define objects and their methods, using `class` declarations, constructors, and methods.

9. What are modules in ES6? How do they work?

   • Answer: ES6 modules allow splitting code into separate files (modules), promoting code reusability and organization. They use `import` and `export` statements to share code between modules.

10. Explain Promises. What are their states?

    • Answer: Promises represent the eventual result of an asynchronous operation. Their states are: pending (initial), fulfilled (successful), or rejected (failed). They handle asynchronous operations more cleanly than callbacks.

11. What is `async`/`await`? How does it simplify asynchronous code?

    • Answer: `async`/`await` makes asynchronous code look and behave a bit more like synchronous code, making it easier to read and write. `async` declares an asynchronous function, and `await` pauses execution until a Promise resolves.

12. Explain Map and Set data structures.

    • Answer: `Map` stores key-value pairs, similar to objects but allowing any data type as keys. `Set` stores unique values of any type.

13. What is the difference between `==` and `===`?

    • Answer: `==` performs loose equality comparison (type coercion), while `===` performs strict equality comparison (no type coercion).

14. Explain the concept of hoisting.

    • Answer: Hoisting is JavaScript's behavior of moving declarations of variables and functions to the top of their scope before code execution. However, only declarations are hoisted, not initializations.

15. What are Symbols in ES6?

    • Answer: Symbols are unique and immutable data types, often used as unique property keys to avoid naming collisions.

16. Explain `Object.assign()` and its uses.

    • Answer: `Object.assign()` copies the values of all enumerable own properties from one or more source objects to a target object. It's used for creating copies of objects and merging objects.

17. What are iterators and generators?

    • Answer: Iterators provide a way to traverse data structures one element at a time. Generators are functions that can pause execution and resume later, yielding values one at a time. They are often used for creating iterators.

18. Explain `Proxy` objects.

    • Answer: `Proxy` objects allow intercepting and customizing operations performed on another object (the target). They can be used for data validation, logging, and other purposes.

19. Explain `Reflect` objects.

    • Answer: `Reflect` provides methods for performing operations on objects that mirror the functionality of Proxy handlers. It helps standardize operations done on objects.

Thank you for reading our blog post on 'ES6 Interview Questions and Answers for internship'.We hope you found it informative and useful.Stay tuned for more insightful content!