fastlane forum text decoder

fastlane-forum-text-decoder.js

const lowerCaseVowels = 'aeiou'
const upperCaseVowels = 'AEIOU'
const lowerCaseConsonants = 'bcdfghjklmnpqrstvwxyz'
const upperCaseConsonants = 'BCDFGHJKLMNPQRSTVWXYZ'

function shiftLeft(needle, haystack) {
  let index = haystack.indexOf(needle)
  if (index === 0) {
    index = haystack.length
  }

  return haystack[index - 1]
}

function decode(input) {
  let chars = input.split('')

  chars = chars.map(char => {
    if (lowerCaseVowels.includes(char)) {
      return shiftLeft(char, lowerCaseVowels)
    }

    if (upperCaseVowels.includes(char)) {
      return shiftLeft(char, upperCaseVowels)
    }

    if (lowerCaseConsonants.includes(char)) {
      return shiftLeft(char, lowerCaseConsonants)
    }

    if (upperCaseConsonants.includes(char)) {
      return shiftLeft(char, upperCaseConsonants)
    }

    return char
  })

  return chars.join('')
}

// source: https://www.thefastlaneforum.com/community/threads/ive-read-the-millionaire-fastlane.28234/post-141911
// remove color:transparent from the block's css to make the text visible and remove user-select:none to be able to copy it
const str = `Sief ov. Muwi vji qesv ecuav jux qiuqmi esi xommoph vu vsefi 5 fezt gus 2 fezt ug gsiifun. Emtu moli jux zua quopv uav vjev zua tjuamfp'v katv hiv opvu e catopitt cetif up "fu xjev zua muwi". O xet duptvepvmz muuloph gus tunivjoph vu fu op vji humg opfatvsz cideati vjev't xjev O muwi vu fu. Pux O lpux O tjuamf katv gudat up nz neop catopitt xjodj emsiefz howit ni ipuahj gsiifun vu qmez humg qsivvz nadj xjipiwis O xepv.`

console.log(decode(str))