Weighted random value in underscore or lodash

random-weighted.coffee

## First you can generate a weighted array

weighted 1: true, 2: false #  [true, false, false]

weighted 1: true, 3: false #  [true, false, false, false]

## Then random picks one randomly
## The following will return true or false with a 1:3 ratio

random weighted 1: true, 3: false


# here's the magic, you need underscore or lodash
weighted = (weightMap) ->
  _ weightMap
    .map (val, weight) -> _.times weight, -> val
    .flatten()
    .value()

random = (arr) -> _.shuffle(arr)[0]

You can replace _.shuffle(arr)[0]by _.pick(arr) I believe!