recursive permutation
function findPerms(str) {
if (str.length === 1) return [str]
let all = []
for (let i = 0; i < str.length; i++) {
const currentLetter = str[i]
const remainingLetters = str.slice(0,i) + str.slice(i+1)
const permsOfRemainingLetters = findPerms(remainingLetters)
permsOfRemainingLetters.forEach(
subPerm => {all.push(currentLetter + subPerm)}
)
}
return all
}