建構式的原型擴充

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# extent 擴充（繼承）
# 在js之中 沒有class概念，但是是拿建構式來實現class
class Animal
  (@name, kind) ->
    @kind = kind
  action: (what) -> "*#{@name} (a #{@kind}) #{what}*"

class Cat extends Animal
  (@name) -> super @name, 'cat'
  purr: -> @action 'purrs'

kitten = new Cat 'Mei'
kitten.purr!      # => "*Mei (a cat) purrs*"

# implements 接口

Huggable =
  hug: -> @action 'is hugged'

class SnugglyCat extends Cat implements Huggable

kitten = new SnugglyCat 'Purr'
kitten.hug!     # => "*Mei (a cat) is hugged*"