Function nextPermutation

src/next-permutation.js:23–39

};

const nextPermutation = a => {
  let smaller = -1;
  for (let i = a.length - 1; i > 0; i -= 1) {
    if (a[i] > a[i - 1]) {
      smaller = i - 1;
      break;
    }
  }
  if (smaller === -1) {
    a.sort((a, b) => a - b);
    return;
  }
  let swapIdx = smaller + 1;
  while (swapIdx < a.length && a[swapIdx] > a[smaller]) swapIdx++;
  swap(a, smaller, swapIdx - 1);
  sort(a, smaller + 1);
};

const a = [1, 2, 3];
console.log([1, 2, 3]);