Properties in CoffeeScript

gistfile1.coffee

# Create a convenient property creator function
Function::property = (properties) ->
  for name, descriptor of properties
    Object.defineProperty @prototype, name, descriptor
  return

# Usage example:
class Circle
  constructor: (@radius) ->

  @property area:
    get: -> @radius * @radius * Math.PI
    set: (a) -> @radius = Math.sqrt(a / Math.PI)

window.c = new Circle(10)
console.assert c.area == 100 * Math.PI
c.area = 1000
console.assert c.area == 1000
console.assert c.radius == Math.sqrt(1000 / Math.PI)