text: Classes in CoffeeScript
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  JavaScript doesn’t have a traditional class system. Instead, it has prototypes. Prototypes can be extremely versatile and powerful, but they’re confusing to novices. Hence, CoffeeScript has created a traditional class system. But… how? CoffeeScript’s catchphrase is “It’s Just JavaScript,” and JavaScript is distinctly missing a traditional class system. In this article, we go over the basics of creating a CoffeeScript class. In the next article, we dig into the (relatively advanced) generated JavaScript to figure out how the magic works.
  The Parent Class
  We’ll do this mostly by example, since it should be fairly easy for those who have read my introductory article on coffeescript to pick up on what’s happening.
  class Bourgeoisie constructor: (@age, @privilegeConstant) -> worry: -> console.log("My stocks are down 1%!") profit: (hardWork, luck) -> return (@age - 23) * hardWork * (luck + @privilegeConstant) elite = new Bourgeoisie(29, 397) elite.worry() # "My stocks are down 1%!" elite.profit(20, 50) #53640
  We declare a class called
  Bourgeoisie. Functions on a class are declared as follows:
  functionName: (arguments) -> code
  The constructor function is named, clearly enough,
  constructor. It takes two arguments,
  age and
  priviligeConstant, and automatically assigns them as instance variables (
  @ is the CoffeeScript replacement for
  this, and when used in the argument of a constructor automatically assigns the variable to the instance). The constructor is called automatically when you create a new
  Bourgeoisie, like at the bottom of the code sample. We also have two other functions. The first,
  worry, takes no arguments. The second,
  profit, takes two arguments and returns a number.
  The Inherited Class
  Now we want to have a class that inherits from
  Bourgeoisie. We’ll call it
  Senator.
  class Senator extends Bourgeoisie worry: -> console.log("The polls are down 1%!") senator = new Senator(45, 992) senator.worry() # "The polls are down 1%!") senator.profit(6, 10) # 132264
  This class extends
  Bourgeoisie, which means that it has all the characteristics of the parent class. The
  constructor and
  profit functions are exactly the same, the only difference is that you make a call to
  Senator instead of
  Bourgeoisie when constructing an instance.
  The
  worry function, on the other hand, is different. The
  Senator worries about polls more than stocks, so his
  worry overwrites that of the parent class. This overwriting is seen again in a
  Student class, shown below.
  class Student extends Bourgeoisie worry: -> console.log("Does my privilege inherently make me complicit in the repression of less fortunate classes?") profit: (hardWork, luck, tuition) -> super(hardWork, luck) - tuition student = new Student(21, 89) student.worry() #"Does my privilege inherently make me complicit in the repression of less fortunate classes?" student.profit(10, 10, 10000) #-11980
  The student’s
  worry overwrites the parent’s
  worry (in an even more dramatic fashion than the Senator’s), and their
  profit is also overwritten. However, the overwrite is now dependent on the parent class’s
  profit function. It takes that and subtracts the tuition. It’s a bad time to be a student! But what you should really learn from this is the
  super keyword, which calls the parent’s version of a function.
  But, I Liked Prototypes
  Good for you! CoffeeScript gives you convenience, but it still leaves you with power. Let’s use it! Here’s our abbreviated example from last time:
  object = (o) -> F = -> F.prototype = o new F() soldier = new Object() soldier.a = jump soldier.r = machineGun sniper = object(soldier) sniper.r = snipe woundedSniper = object(sniper) woundedSniper.a = -> console.log('aaaargh my leg!') woundedSoldier = object(soldier) woundedSoldier.a = woundedSniper.a
  This should seem familiar, because 90% of the change was replacing a few
  function‘s with pointy arrows. The prototypical inheritance system is untouched because, remember, CoffeeScript is just JavaScript. The syntax is cleaner, and there is nothing more to learn if you want to implement prototypes in the Brendan Eich style we used last time. That’s not to say that CoffeeScript doesn’t apply some shortcuts. You can use
  :: instead of
  prototype. However, in the Brendan Eich style of prototypes, we only need to use that once, in the
  object(o) method. We can also access the
  extends and
  super keywords, but those are used only in constructors – which we have once again hidden away in the
  object(o) method.
  Conclusion
  The classical inheritance system in CoffeeScript provides convenience and comfort to the average developer. In addition, the cleaner syntax of CoffeeScript makes implementing a true prototypal system slightly easier. There’s simply no way to lose.
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