random-letter-generator.js

;(function (namespace) {
  'use strict'

  namespace.randomlettergenerator = function (namespace) {
    var total = 0
    var lettersArray = []

    /*
     * Populates "lettersArray" and computes "total".
     */
    ;(function () {
      var letters = {}
      namespace.dictionaries.forEach(function (word) {
        var i, len, letter
        for (i = 0, len = word.length; i < len; i++) {
          letter = word[i]
          if (typeof letters[letter] === 'undefined') {
            letters[letter] = { letter: letter, count: 1 }
            lettersArray.push(letters[letter])
          } else {
            letters[letter].count += 1
          }
          total += 1
        }
      })
    }())

    /*
     * Sorts by descending letter frequency
     */
    lettersArray.sort(function (a, b) {
      if (a.count > b.count) {
        return -1
      }
      if (a.count < b.count) {
        return 1
      }
      return 0
    })

    /**
     * Random letter generator.
     */
    function RandomLetterGenerator () {
      this.lastIx = -1
    }

    /**
     * Returns a random letter.
     *
     * @return Random letter.
     */
    RandomLetterGenerator.prototype.next = function () {
      var i = this.lastIx + 1
      var len = lettersArray.length
      var count = Math.random() * total

      while (count > 0) {
        if (i >= len) {
          i = 0
        }
        count -= lettersArray[i].count
        i++
      }

      this.lastIx = i
      return lettersArray[i].letter
    }

    namespace.RandomLetterGenerator = RandomLetterGenerator
  }
}((function () {
  if (typeof window === 'undefined') {
    return module.exports
  } else {
    return window
  }
}())))