PowerSet.js

function PowerSet(str) {
  let result = [] 
  
  function constructSubSet(subSet, index) {
    if(index >= str.length) {
      result.push(subSet)
      return
    }
    constructSubSet(subSet, index + 1)
    constructSubSet(subSet + str[index], index + 1)
  }
  
  constructSubSet("", 0)
  return result
}