super reduced string

reducedString.js

// versao one line
const str = 'aaabccddd'
str.split('').reduce((acc, res) => res == acc.slice(-1)[0] ? acc.slice(0, -1) : acc.concat(res), []).join('') || 'Empty String' //'abd'

//versao composed
const lastItem = arr => arr.slice(-1)[0]
const removeLast = arr => arr.slice(0, -1)

const reduceArray = arr => {
  return arr.reduce((acc, res) => res == lastItem(acc) ? removeLast(acc) : acc.concat(res), [])
}

const applyFunctionToStrAsArr = (str, func) => {
  return func(str.split('')).join('')
}

const checkIfNotEmpty = str => str || 'Empty String'
const compose = str => checkIfNotEmpty(applyFunctionToStrAsArr(str, reduceArray))
//compose(str) //'abd'