Reducer library for JS

reducer-lib.js

const sumReducer = (sum, x) => sum + x;

const minReducer = (min/* =null */, x) => {
  if (min == null) return x;
  return min < x ? min : x;
};
const maxReducer = (max/* =null */, x) => {
  if (max == null) return x;
  return max > x ? max : x;
};
const meanReducer = (total, amount, index, array) =>
  (index === array.length - 1
    ? (total + amount) / array.length
    : total + amount);

const ascendingSort = (a, b) => {
  if (a < b) return -1;
  if (a > b) return 1;
  return 0;
};

const descendingSort = (a, b) => {
  if (a < b) return 1;
  if (a > b) return -1;
  return 0;
};