JavaScript 商店脚本无法按预期运行

Question

我正在尝试让这个商店脚本包含以下条件：

1. 余额不能低于0
2. 资金不足时，将使用代金券。
3. 它记录凭证的使用和成功确认。

现在余额确实低于零，代金券也没有被使用……也许这很明显，但我被逼疯了。

另外，有什么技巧可以优化这段代码吗？

谢谢！如果这非常明显，我很抱歉。我对此完全陌生！

var total = 500;
var balance = 400;
var voucher = 100;
useVoucher = true;

if ( (total > balance) || (balance < 0) ) {
console.log("Insufficient funds. The total is " + total + "$ and you only have a balance of " + balance + "$.");
} else if (useVoucher = true) {
total = total - voucher
console.log(voucher + "$ Voucher applied. The new total is " + total + "$.");
} else {
console.log("You can't afford this item");
} 

if ((balance - total < 0) && balance > total); {
console.log("Success! You have a new balance of " + (balance - total) + "$.");
}

Answer 1

首先您必须检查是否可以使用优惠券。如果您没有足够的余额，但您使用代金券有足够的余额，就会发生这种情况。

在这种情况下使用代金券。

然后检查您是否有足够的余额来支付。

代码如下：

var total = 500;
var balance = 400;
var voucher = 100;
useVoucher = true;


if (total > balance     // Not enough balance
      && useVoucher     // You can use the voucher
      && total - voucher <= balance) {  // Total minus voucher is under balance
  console.log(voucher + "$ Voucher applied. The new total is " + total + "$.");
  // IN this case use voucher
  total = total - voucher;

  // Would be better to check here if total is under 0, 
  // otherwise in the next few lines of code you will increase your balance.
} 

if (total <= balance) {   // Check if you have enough balance
  balance = balance - total;
  console.log("Success! You have a new balance of " + balance + "$.");
} else {                  // Not enough balance
  console.log("Insufficient funds. The total is " + total + "$ and you only have a balance of " + balance + "$.");
}

应进行额外检查以检查代金券是否大于总数。通常使用代金券如果大于价格，您会损失代金券的额外金额，但在这种情况下我没有添加这个检查，因为它没有明确要求。

Answer 2

有几个错误，这里是修正版：

var total = 500;
var balance = 400;
var voucher = 100;
useVoucher = true;

if ( (total > balance) || (balance < 0) ) {
    console.log("Insufficient funds. The total is " + total + "$ and you only have a balance of " + balance + "$.");
} else if (useVoucher) {
    total = total - voucher
    console.log(voucher + "$ Voucher applied. The new total is " + total + "$.");
} else {
    console.log("You can't afford this item");
} 

if ((balance - total > 0) > 0 && balance > total) {
    console.log("Success! You have a new balance of " + (balance - total) + "$.");
}

1. 不要在if 语句中使用;。这不是必需的，会导致您的逻辑被错误地执行。
2. 不要执行(useVoucher = true)，这会将值true 分配给变量useVoucher，而不是检查它是否为true。请改用(useVoucher)。这将检查 useVoucher 的值是否不等于 false。

Answer 3

再次尝试检查您的逻辑。似乎只有在有足够资金的情况下才会使用代金券。我认为您应该删除“else if”逻辑并在第一个“if”块中输入凭证使用情况。

Answer 4

debugger;
var total = 500;
var balance = 400;
var voucher = 100;
var balanceWithVoucher = balance + voucher;
total > balance ? useVoucher = true : useVoucher = false;


if ((total > balance && total > balanceWithVoucher) || (balance < 0)) {
    console.log("Insufficient funds. The total is " + total + "$ and you only have a balance of " + balance + "$.");
} else if (useVoucher == true) {
    total = total - voucher
    console.log(voucher + "$ Voucher applied. The new total is " + total + "$.");
} else {
    console.log("You can't afford this item");
}
if ((balance - total > 0) && balance > total); {
    console.log("Success! You have a new balance of " + (balance - total) + "$.");
}