CoffeeScript Interview Questions and Answers for freshers

1. What is CoffeeScript?

   • Answer: CoffeeScript is a little language that compiles into JavaScript. It aims to provide a cleaner, more readable syntax while maintaining the full power and flexibility of JavaScript.

2. What are the key advantages of using CoffeeScript?

   • Answer: Increased code readability, reduced boilerplate code, cleaner syntax (eliminating semicolons, parentheses in some cases), and easier integration with existing JavaScript libraries and frameworks.

3. How does CoffeeScript handle indentation?

   • Answer: CoffeeScript uses indentation to define code blocks, similar to Python. Consistent indentation is crucial; inconsistent indentation will lead to compilation errors.

4. Explain the concept of implicit returns in CoffeeScript.

   • Answer: The last expression in a CoffeeScript function is implicitly returned. You don't need an explicit `return` statement in many cases.

5. How do you define a function in CoffeeScript?

   • Answer: You can define functions using `->` (fat arrow) or `=>` (thin arrow for single-line functions): `add = (a, b) -> a + b`

6. What are list comprehensions in CoffeeScript? Provide an example.

   • Answer: List comprehensions provide a concise way to create arrays. Example: `squares = (x*x for x in [1..5])`

7. How do you handle classes and inheritance in CoffeeScript?

   • Answer: CoffeeScript uses a class-based syntax inspired by Ruby. You define classes using the `class` keyword and inheritance using `extends`.

8. Explain the difference between `->` and `=>` in CoffeeScript functions.

   • Answer: `->` creates a multi-line function, while `=>` creates a single-line function (implicitly returning the expression).

9. How do you define a CoffeeScript object literal?

   • Answer: Similar to JavaScript, but often more concise. Example: `person = {name: "Alice", age: 30}`

10. What is the purpose of the `unless` keyword in CoffeeScript?

    • Answer: `unless` is the opposite of `if`; it executes a block of code only if a condition is *false*.

11. Explain how to use loops (for and while) in CoffeeScript.

    • Answer: CoffeeScript provides `for` loops similar to JavaScript, `while` loops function similarly to other languages. Example: `for i in [0...10] ...`

12. How do you handle conditional statements (if/else) in CoffeeScript?

    • Answer: Similar to JavaScript, but often more concise due to implicit returns and indentation. Example: `if condition then doSomething()`

13. What are splat arguments in CoffeeScript? Give an example.

    • Answer: Splat arguments allow a function to accept a variable number of arguments. Example: `sum = (a, b, ...rest) -> a + b + rest.reduce((a,b) -> a + b, 0)`

14. Explain the use of the `switch` statement in CoffeeScript.

    • Answer: CoffeeScript's `switch` statement is similar to JavaScript's, but uses indentation to define cases.

15. How do you handle exceptions (try/catch) in CoffeeScript?

    • Answer: CoffeeScript supports `try...catch` blocks for exception handling, similar to JavaScript.

16. How can you compile CoffeeScript code?

    • Answer: You can compile CoffeeScript using the command-line compiler (`coffee -c`) or various build tools like Grunt or Gulp.

17. What are some common CoffeeScript pitfalls to avoid?

    • Answer: Inconsistent indentation, misunderstanding implicit returns, and forgetting to compile before running in a browser.

18. How does CoffeeScript handle closures?

    • Answer: CoffeeScript handles closures the same way JavaScript does; inner functions have access to variables in their surrounding scope.

19. Explain the concept of destructuring in CoffeeScript. Give an example.

    • Answer: Destructuring allows you to easily extract values from objects and arrays. Example: `{name, age} = {name: "Bob", age: 40}`

20. How do you work with regular expressions in CoffeeScript?

    • Answer: Regular expressions work the same way as in JavaScript, using the `/regex/` notation.

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