A tiny module to calculate how many Walters you can afford.

walter-calculator.js

const WALTER_PRICE = 0.53;
const TARE_PRICE = 0.08;

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

function getNumWalters(money) {
  var ret = [0, 0];
  ret[0]=Math.floor(money/WALTER_PRICE);
  ret[1]=round(money-ret[0]*WALTER_PRICE);
  return ret;
}

/**
 * Main function
 *
 * @param money number
 * @returns array [total walters, money left]
 */
function init(money) {
  // TODO: validation
  // - float?
  // - abs?
  // - significant figures

  return new Promise((resolve) => {
    let totalWalters = 0;
    while (money >= WALTER_PRICE) {
      var walters = getNumWalters(money);

      totalWalters += walters[0];
      money = round(walters[1] + TARE_PRICE * walters[0]);
    }

    return resolve([totalWalters, money]);
  });
}

// console.log('1', init(1));
// console.log('2', init(2));

init(77).then((value) => {
  console.log('77', value);
});

module.exports = init;