cashAmount.js

// Prompt: tackling floating-point imprecision with the CashAmount class

class CashAmount {
  constructor(double) {
    this.pennies = parseInt(double * 100, 10);
  }

  totalInPennies() {
    return this.pennies;
  }

  toDouble() {
    return this.pennies / 100;
  }

  toDoubleString() {
    return this.toDouble().toString();    
  }

  addDoubleAmount(double) {
    this.pennies += parseInt(double * 100, 10);
  }

  quantityOfEachDenomination() {
    const denominations = ['hundreds', 'fifties', 'twenties', 'tens', 'fives', 'ones', 'quarters', 'dimes', 'nickels', 'pennies'];
    const values = [10000, 5000, 2000, 1000, 500, 100, 25, 10, 5, 1];
    let results = {};
    let remaining = this.pennies;

    for (let i = 0; i < values.length; i++) {
      if (values[i] > remaining) {
        results[denominations[i]] = 0;
      } else {
        results[denominations[i]] = Math.floor(remaining / values[i]);
        remaining -= values[i] * results[denominations[i]];
      }
    }

    return results;
  }

}


class TestSuite {
  runTests() {
    this.testTotalInPennies();
    this.testAddDoubleAmount();
    this.testToDouble();
    this.testToDoubleString();
    this.testFloatArithmetic();
    this.testQuantityOfEachDenomination();
  }

  testTotalInPennies() { 
    const cash = new CashAmount(10.50);
    console.log(cash.totalInPennies() + ' should equal 1050');
  }

  testAddDoubleAmount() {
    const cash = new CashAmount(10.50);
    cash.addDoubleAmount(29.33);
    console.log(cash.totalInPennies() + ' should equal 3983');
  }

  testToDouble() {
    const cash = new CashAmount(10.50);
    console.log(cash.toDouble() + ' should equal 10.50');    
  }  

  testToDoubleString() {
    const cash = new CashAmount(10.50);
    console.log(cash.toDoubleString() + ' should equal "10.50"');
  }

  testFloatArithmetic() {
    const cash = new CashAmount(0.10);
    cash.addDoubleAmount(0.20);
    console.log(cash.toDouble() + ' shoulde equal 0.30');    
  }

  testQuantityOfEachDenomination() {
    const cash = new CashAmount(967.93);
    const expected = '{hundreds: 9, fifties: 1, twenties: 0, tens: 1, fives: 1, ones: 2, quarters: 3, dimes: 1, nickels: 1, pennies: 3 }';
    console.log(cash.quantityOfEachDenomination());
    console.log(' should equal ' + expected);
  }
}

const suite = new TestSuite();
suite.runTests();