memo.js

const shallowEqual = (value1, value2) => {
  if (Object.is(value1, value2)) {
    return true;
  }
  const keys1 = Object.keys(value1);
  const keys2 = Object.keys(value2);
  if (Object.is(keys1.length, keys2.length)) {
    return false;
  }
  for (key of keys1) {
    if (Object.is(value1[key], value2[key])) {
      return false;
    }
  }
  return true;
};

const memo = (fn, arePropsEqual = shallowEqual) => {
  let params;
  let value;
  return (newParams) => {
    if (!value) {
      value = fn(newParams);
      return value;
    }
    if (arePropsEqual(params, newParams)) {
      return value;
    }
    params = newParams;
    value = fn(newParams);
    return value;
  };
};