Find all unique substrings of a string

substring.js

const findUniqueSubstrings = (str) => {
  const arr = [...str].reduce((acc, _, idx) =>
    acc.concat(Array.from({length: str.length}, (_, innerIdx) =>
      str.substring(idx, innerIdx + 1)
    )), [])
  return new Set(arr)
}

findUniqueSubstrings("Your string here")