AllSets

AllSets.js

function allSets (arr) {
  const target = Math.pow(2, arr.length) - 1;
  const all = [];
  for (let i = 1; i <= target; i++) {
    all.push(Array.from({length: arr.length}, (v, index) => i & (1 << index) ? arr[index] : null).filter(v => arr.indexOf(v) > -1)); 
  }
  console.log(all);
}

function allSetsRec (arr, index, set, all) {
  if (index === arr.length) {
    all.push(set);
    return;
  }
  all = all || [];
  index = index || 0;
  set = set || [];
  as(arr, index + 1, set, all);
  as(arr, index + 1, set.concat(arr[index]), all);
  console.log(all);
}