Extending JavaScript's Array object in CoffeeScript

array_tweaks.coffee

class Array
  all: (f)->
    for e in this
      return false unless f(e)
    true

  any: (f)->
    for e in this
      return true if f(e)
    false
    
  reduce: (f)->
    accum = f(this[0], this[1])
    
    for e in this[2..-1]
      accum = f(accum, e)
    
    accum
    
  sum: ->
    this.reduce (a,b)-> a + b
    
  sum_by: (f)->
    this.reduce (a,b)-> 
      f(a) + f(b)


alert [1,2,3,4].sum()
alert [1,2,3,4].reduce( (a,b)-> a + b )
alert [1,2,3,4].sum_by( (x)-> x * 2 )