Probability Map

probabilityMap.js

class ProbabilityMap {
  constructor (map) { // map = {foo: 32, bar: 21}
    this.calculateSize = () => {
      let count = 0
      for (let [,value] of this.set) {
        count += value
      }
      return count
    }
    this.set = map ? new Map(Object.entries(map)) : new Map()
    this.size = map ? this.calculateSize() : 0
    this.increment = (key) => {
      this.size++
      if (this.set.has(key)) this.set.set(key, this.set.get(key) + 1)
      else this.set.set(key, 1)
    }
    this.pick = () => {
      let pick = this.size * Math.random()
      for (let [key, value] of this.set) {
        pick -= value
        if (pick < 0) return key
      }
    }
  }
}