const assert = require("assert").strict;

const ITEMS = {
  お茶: 120,
  コーラ: 150,
  エナジードリンク: 280,
};

const CURRENCY = {
  '1000': 0,
  '500': 0,
  '100': 0,
  '50': 0,
  '10': 0,
};

function calcChange(item, paidMoney) {
  if (!Object.keys(ITEMS).includes(item)) throw 'Error';

  let result = paidMoney - ITEMS[item];
  const x = Object.fromEntries(
    Object.keys(CURRENCY)
      .sort((a, b) => b - a)
      .map((x) => {
        const value = result;
        result = Math.floor(value % Number(x));
        return [x, Math.floor(value / Number(x))];
      }),
  );

  return x;
}

const expected = {10: 3, 50: 1, 100: 3, 500: 1, 1000: 0};
assert.deepEqual(calcChange('お茶', 1000), expected);