javascript - 我为 Freecodecamp 创建了一个 "Cash Register"函数，但出于某种原因，最后两个测试没有通过？

Question

我创建了这个函数但是最后两个测试

checkCashRegister(19.5, 20, [["PENNY", 0.01], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 1], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]) should return {status: "INSUFFICIENT_FUNDS", change: []}.
checkCashRegister(19.5, 20, [["PENNY", 0.5], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]) should return {status: "CLOSED", change: [["PENNY", 0.5], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]}.

不要通过。我的代码有什么问题？

任务是:

Design a cash register drawer function checkCashRegister() that accepts purchase price as the first argument (price), payment as the second argument (cash), and cash-in-drawer (cid) as the third argument.

cid is a 2D array listing available currency.

The checkCashRegister() function should always return an object with a status key and a change key.

Return {status: "INSUFFICIENT_FUNDS", change: []} if cash-in-drawer is less than the change due, or if you cannot return the exact change.

Return {status: "CLOSED", change: [...]} with cash-in-drawer as the value for the key change if it is equal to the change due.

Otherwise, return {status: "OPEN", change: [...]}, with the change due in coins and bills, sorted in highest to lowest order, as the value of the change key.

我的代码:

const INSUFFICIENT_FUNDS = {
  status: 'INSUFFICIENT_FUNDS',
  change: []
};
const CLOSED_CID = {
  status: 'CLOSED',
  change: []
};
const POSITION_CID = [
  ['ONE HUNDRED', 100],
  ['TWENTY', 20],
  ['TEN', 10],
  ['FIVE', 5],
  ['ONE', 1],
  ['QUARTER', 0.25],
  ['DIME', 0.1],
  ['NICKEL', 0.05],
  ['PENNY', 0.01]
];
const add = (a, b) => a + b[1];
const checkCashRegister = (price, cash, cid) => {
  let finalChange = [];
  let changeDue = cash - price;
  const cidSum = cid.reduce(add, 0).toFixed(2);
  /*
  If there is exactly enough money to provide change, the
  status key is “CLOSED”, and the change key is our
  cash-in-drawer(cid).
  */
  if (cidSum == changeDue) {
    return {
      CLOSED_CID,
      change: cid
    };
  }
  /*
  If there is not enough money to provide change, the status key
  is “INSUFFICIENT_FUNDS” and the change key is an empty array.
  */
  if (cidSum < changeDue) {
    return INSUFFICIENT_FUNDS;
  }
  /*
  If there is enough money to provide change with money still
  left in the drawer, the change is then provided by going down
  a list of currency units from high to low, pushing them to
  the change array, and subtracting them from both the cash
  owed and the cash-in-drawer(cid).
  */
  let cidReverse = cid.reverse();
  POSITION_CID.map((posCid, index) => {
    const billValue = posCid[1];
    while (changeDue >= billValue && cidReverse[index][1] >= billValue) {
      changeDue -= billValue; // minus change due from bill value
      changeDue = changeDue.toFixed(2); // fix rounding errors
      const hasBillValueAlready = finalChange.filter(p => p[0] === cidReverse[index][0]);
      if (hasBillValueAlready.length > 0) {
        finalChange = finalChange.map(k => (k[0] === posCid[0] && [k[0], (k[1] += billValue)]) || [k[0], k[1]]);
      } else {
        finalChange.push([cidReverse[index][0], billValue]);
      }
      cidReverse[index][1] -= billValue; // minus bill value from cash-in-drawer
    }
  });
  if (changeDue !== 0) {
    return {
      status: 'OPEN',
      change: finalChange
    };
  } else {
    return INSUFFICIENT_FUNDS;
  }
};
const price = 19.5;
const cash = 200;
const cid = [
  ['PENNY', 1.01],
  ['NICKEL', 2.05],
  ['DIME', 3.1],
  ['QUARTER', 4.25],
  ['ONE', 90],
  ['FIVE', 55],
  ['TEN', 20],
  ['TWENTY', 60],
  ['ONE HUNDRED', 100]
];
// checkCashRegister(price, cash, cid);

console.log(
checkCashRegister(19.5, 20, [
  ["PENNY", 1.01],
  ["NICKEL", 2.05],
  ["DIME", 3.1],
  ["QUARTER", 4.25],
  ["ONE", 90],
  ["FIVE", 55],
  ["TEN", 20],
  ["TWENTY", 60],
  ["ONE HUNDRED", 100]
]),
checkCashRegister(19.5, 20, [["PENNY", 0.01], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 1], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]),"should return", `{status: "INSUFFICIENT_FUNDS", change: []}`,
checkCashRegister(19.5, 20, [["PENNY", 0.5], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]), "should return", `{status: "CLOSED", change: [["PENNY", 0.5], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]}`)

Answer 1

需要解决的两个问题:

• 当应找零正好是收银机中的零钱时，代码会返回一个结构不正确的对象:

  return {
    CLOSED_CID,
    change: cid
  };
  

  这将创建一个属性 CLOSED_CID，它的值是一个具有嵌套的 status 和 change 属性的对象...您还可以添加父级别的另一个 change 属性。相反，您应该忘记预定义的 CLOSED_CID 对象，然后执行以下操作:

  return {
    status: "CLOSED",
    change: cid
  };
  

• 是否返回状态OPEN 或INSUFFICIENT_FUNDS 的决定应该在相反的条件下。当您将所有 的更改金额归因于您应该返回OPEN 的账单时。所以改变这个:

  if (changeDue !== 0) {
    return {
      status: 'OPEN',
      change: finalChange
    };
  } else {
    return INSUFFICIENT_FUNDS;
  }
  

  到:

  if (changeDue == 0) { // All change could be translated to available bills/coins
    return {
      status: 'OPEN',
      change: finalChange
    };
  } else { // There is change remaining that cannot be covered by available bills/coins
    return INSUFFICIENT_FUNDS;
  }
  

备注:toFixed 方法返回一个字符串。最好将结果显式转换回数字数据类型。目前在您的代码中没有问题，因为当您执行 -= 和 == 时该转换会隐式发生，但出于代码维护的原因，您最好不要依赖在那上面。因此，每当您调用 toFixed 时添加一元 +:

const cidSum = +cid.reduce(add, 0).toFixed(2);
// ...
changeDue = +changeDue.toFixed(2);

然而，我会建议以美分进行所有计算，因此所有计算都是使用整数值完成的，这不会受到您需要处理的不精确性的影响。

我假设您已经找到了解决方案 on the web , 还有 many Q&A on Stack Overflow关于同样的挑战。