Hiring guide for CoffeeScript Engineers

CoffeeScript Developer Hiring Guide

CoffeeScript is a programming language that compiles into JavaScript, conceived by Jeremy Ashkenas in 2009. It adds syntactic sugar inspired by Ruby, Python and Haskell to enhance JavaScript's brevity and readability. The language has been popular for web development due to its close relationship with JavaScript - one of the core technologies of the World Wide Web. CoffeeScript also influenced the development of later languages like TypeScript and Dart. Its source code was made available on GitHub, fostering an active community around it.

Ask the right questions secure the right CoffeeScript talent among an increasingly shrinking pool of talent.

First 20 minutes

General CoffeeScript app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in CoffeeScript application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

What are the differences between CoffeeScript and JavaScript?
CoffeeScript is a programming language that transcompiles to JavaScript. The main differences are: CoffeeScript has a cleaner syntax, it removes the need for semicolons and parentheses, it supports string interpolation, it has a safer scope handling with the use of 'do', and it has a more comprehensive loop and comprehension syntax.
How would you compile a CoffeeScript file into JavaScript?
You can compile a CoffeeScript file into JavaScript using the CoffeeScript compiler. The command is 'coffee --compile filename.coffee'. This will create a filename.js file with the compiled JavaScript.
What are the advantages of using CoffeeScript over JavaScript?
CoffeeScript has a more readable and succinct syntax, it has additional features not present in JavaScript like array comprehensions and destructuring assignment, and it helps to write safer JavaScript by preventing common mistakes.
How would you handle exceptions in CoffeeScript?
Exceptions in CoffeeScript can be handled using the 'try/catch/finally' blocks, similar to JavaScript. The syntax is 'try expression catch error then expression'.
What is the purpose of the 'fat arrow' (=>) in CoffeeScript and how does it differ from the 'thin arrow' (->)?
In CoffeeScript, the 'fat arrow' (=>) is used to define a function that is bound to the current value of 'this', while the 'thin arrow' (->) defines a function without binding 'this'. This is useful when working with callbacks or event handlers where the context is important.
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What you’re looking for early on

Does the candidate have a strong understanding of CoffeeScript syntax and structure?
Has the candidate demonstrated experience with using CoffeeScript in a professional setting?
Can the candidate solve problems using CoffeeScript?
Does the candidate understand how to use CoffeeScript in conjunction with other technologies?

Next 20 minutes

Specific CoffeeScript development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you create a class in CoffeeScript?
In CoffeeScript, you can create a class using the 'class' keyword, followed by the name of the class. You can also define a constructor using the 'constructor' keyword. For example, 'class MyClass constructor: (@name) ->'.
What is the use of the '@' symbol in CoffeeScript?
In CoffeeScript, the '@' symbol is a shorthand for 'this.'. It is used to refer to the current object. It can also be used in the constructor to automatically create instance variables.
How would you create a private method in a CoffeeScript class?
In CoffeeScript, all methods are public by default. To create a private method, you can define it outside the class and then call it from within the class.
Describe the difference between '==', '===', 'is' and 'isnt' operators in CoffeeScript.
In CoffeeScript, '==' and '===' are replaced by 'is'. It checks for equality including type. '!=' and '!==' are replaced by 'isnt'. It checks for inequality. CoffeeScript does not have '==' and '===' operators.
How would you use mixins in CoffeeScript?
Mixins in CoffeeScript can be implemented by extending the prototype of a class with the properties and methods of another object. The 'extend' function from Underscore.js or jQuery can be used for this purpose.
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The ideal back-end app developer

What you’re looking to see on the CoffeeScript engineer at this point.

At this point, a skilled CoffeeScript engineer should demonstrate strong problem-solving abilities, proficiency in CoffeeScript programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with CoffeeScript.

What does the following CoffeeScript code do?
`x = 10`
This code declares a variable named 'x' and assigns it the value 10.
What will be the output of the following CoffeeScript code?
`a = 5
b = 10
console.log a + b`
The output will be 15. This code declares two variables 'a' and 'b', assigns them the values 5 and 10 respectively, and then prints the sum of 'a' and 'b'.
What does the following CoffeeScript code do?
`arr = [1, 2, 3, 4, 5]
newArr = (num for num in arr when num % 2 == 0)`
This code creates a new array 'newArr' that contains only the even numbers from the original array 'arr'.
What will be the output of the following CoffeeScript code?
`doSomething = () ->
  setTimeout (-> console.log 'Hello'), 1000
console.log 'Goodbye'
The output will be 'Goodbye' followed by 'Hello' after a delay of one second. The 'doSomething' function uses a setTimeout to delay the console.log 'Hello' by 1000 milliseconds.

Wrap-up questions

Final candidate for CoffeeScript Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle CoffeeScript application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What is the purpose of the 'do' keyword in CoffeeScript?
The 'do' keyword in CoffeeScript is used to immediately invoke a function. It can also be used to create a new scope, which is useful to capture the current value of a variable in a loop.
How would you use the 'splats' (...) operator in CoffeeScript?
The 'splats' operator in CoffeeScript is used to handle function arguments that can be of any number. It can be used in function definition, function invocation, array literals and destructuring assignment.
Describe the difference between 'let' and 'var' in CoffeeScript.
CoffeeScript does not have 'let' and 'var'. Instead, it uses the '=' operator to declare variables. The scope of the variable is determined by the indentation level.

CoffeeScript application related

Product Perfect's CoffeeScript development capabilities

Beyond hiring for your CoffeeScript engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in CoffeeScript projects, and can engage in multiple capacities.