processWords.js

// library imports 😜 wink, wink
const identity = x => x
const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)))

function process (words, configs) {
  const lengthFilter = length => word =>
    Array.isArray(length)
      ? word.length >= length[0] && word.length <= length[1]
      : word.length === length

  const strip = what => word => {
    const regexes = {
      vowels: /[aeiou]/gi,
      consonants: /[^aeiou]/gi
    }

    return word.replace(regexes[what], '')
  }

  const upperCase = what => word => {
    const indexes = {
      first: 0,
      last: word.length - 1
    }

    return word
      .split('')
      .map((char, index) => indexes[what] === index
        ? char.toUpperCase()
        : char
      )
      .join('')
  }

  return configs.map(config =>
    words
      .filter(lengthFilter(config.length))
      .map(compose(
        config.upperCase ? upperCase(config.upperCase) : identity,
        config.strip ? strip(config.strip) : identity
      ))
  )
}

var words = [
  'spacejump',
  'apples',
  'graphics',
  'javascript',
  'peaches'
]

var configs = [
  {
    upperCase: 'first',
    length: [6, 8]
  },
  {
    upperCase: 'last',
    length: [7, 9],
    strip: 'vowels'
  },
  {
    length: 10,
    strip: 'consonants'
  }
]

console.log(process(words, configs))