Pattern

pattern.js

const items =　[1, 2, 3];

function pattern(items, paths, results) {
  if (items.length === 0) {
    results.push([ ...paths ]);
    return results
  }
  let curr = results;
  for (let i = 0; i < items.length; i++) {
    paths.push(items[i]);
    curr = pattern(items.filter(item => item != items[i]), paths, curr);
    paths.pop();
  }
  return curr;
}

function allPattern(items) {
  return pattern(items, [], []);
}

const results = allPattern(items);

console.log(results);
console.log(results.length);