calculator.js

'use strict';

const WALTER_PRICE = 0.53;
const TARE_PRICE = 0.08;

export default function WalterCalculator(money) {
    const ret = { totalWalters: 0, leftoverMoney: 0 };

    console.log('End');
    return new Promise(function(resolve) {
        if (money < WALTER_PRICE) {
            ret.totalWalters = 0;
            ret.leftoverMoney = money;
        }

        while (money >= WALTER_PRICE) {
            const {numWalters, leftoverMoney} = getNumWalters(money);
            ret.totalWalters += numWalters;
            money = round(leftoverMoney + TARE_PRICE * numWalters);
        }

        ret.leftoverMoney = money;
        resolve(ret);
    });
}

function getNumWalters(money) {
    const ret = { numWalters: 0, leftoverMoney: 0 };
    ret.numWalters = Math.floor(money/WALTER_PRICE);
    ret.leftoverMoney = round(money-ret.numWalters*WALTER_PRICE);

    return ret;
}

function round(f) {
    return Math.round(f*Math.pow(10,2))/Math.pow(10,2);
}