오브젝트의 가중치에따라 렌덤하게 선택함

rand sort.coffee

banners = [
    priority:10
  ,
    priority:10
  ,
    priority:20
  ,
    priority:30
  ,
    priority:40
]
banner = do (banners)->
  total = []
  for banner,i in banners
    for _ in [1..banner.priority]
      total.push i
  banners[total[Math.floor(Math.random() * total.length)]]
console.log banner

cyluss횽의 코드에서 몇개 훔쳐왔음!