Question

我是javascript的新手，目前正在编写一个在终端中运行的基本文件。其中大部分是有效的。它允许用户添加信用/删除信用并检查他们的信用。最后一部分是允许他们购买产品，并将这笔金额从他们的整体信贷中删除。

我遇到的问题是，它确实显示购买商品时已删除金额。返回菜单并在之后检查剩余信用额时，它将返回原始金额。

我尝试使用下面的代码来保存信用额度（即使在检查可用信用额后也会这样做）：

    credit -= readlineSync.keyInSelect(products, 'What product would you like?');

但是因为数组使用了用户输入的数字，所以它从整体信用中删除该数字而不是实际价格。因此，例如，如果用户选择选项4，它将从信用卡中删除4，而实际上Candy是3英镑。

我将非常感谢任何可以给予的帮助，因为我花了很长时间没有找到解决方案。

Answer 1

问题是您在购买产品后从不更新信用下面这一行所做的就是他们对你做了多少工作吧:)）

console.log('Thank you, your Candy has now been dispensed. Your total credit is now £' + (credit - removeCredit - 3));

解决方案非常简单，更新信用，然后显示它们，例如：

if (index == 3) {
    credit = credit - 4;
    console.log('Thank you, your Candy has now been dispensed. Your total credit is now £' + credit);
}

所以你的代码应该是

 var readlineSync = require('readline-sync');
 var credit = 0;
 var removeCredit = 0;

 menu = [];
 menu[0] = "Purchase a product";
 menu[1] = "View your credit";
 menu[2] = "Add credit";
 menu[3] = "Retrieve a refund";
 menu[4] = "Quit!";

 products = [];
 products[0] = "Drink: £1";
 products[1] = "Crisps: £1";
 products[2] = "Chocolate: £2";
 products[3] = "Candy: £3";

 do {
     index = readlineSync.keyInSelect(menu, 'Please choose your option');
     if (index == 1) {
         console.log("The total amount of credit you have is: £", credit);
     }

     if (index == 2) {
         credit += readlineSync.questionInt('How much credit would you to purchase? ');
         console.log("The total amount of credit you have is: £" + credit);
     }

     if (index == 3) {
         credit -= readlineSync.questionInt('How much credit would you like to remove? ');
         console.log("This credit has now been removed, your total available credit is: £" + credit);
     }
     if (index == 0) {
         index = readlineSync.keyInSelect(products, 'What product would you like?');
         if (index == 0) {
            credit = credit - 1;
            console.log('Thank you, your Drink has now been dispensed. Your total credit is now £' + credit);
         }
         if (index == 1) {
            credit = credit - 1;
            console.log('Thank you, your Crisps have now been dispensed. Your total credit is now £' + credit);
         }
         if (index == 2) {
            credit = credit - 2;
            console.log('Thank you, your Chocolate has now been dispensed. Your total credit is now £' + credit);
         }
         if (index == 3) {
            credit = credit - 3;
            console.log('Thank you, your Candy has now been dispensed. Your total credit is now £' + credit);
         }
     }
 } while (index != 4)

Answer 2

我稍微清理了你的代码并修复了你观察到的问题：

var readlineSync = require('readline-sync');
var credit = 0;
var index;

var menu = [
    'Purchase a product',
    'View your credit',
    'Add credit',
    'Retrieve a refund',
    'Quit!'
];

var products = [
    'Drink',
    'Crisps',
    'Chocolate',
    'Candy'
];

var prices = [1, 1, 2, 3];

var productList = products.map(function(product, i) {
    return product + ': £' + prices[i];
});

do {
    index = readlineSync.keyInSelect(menu, 'Please choose your option');

    if (index == 1) {
        console.log('The total amount of credit you have is: £%d', credit);
    }

    if (index == 2) {
        credit += readlineSync.questionInt('How much credit would you to purchase? ');
        console.log('The total amount of credit you have is: £%d', credit);
    }

    if (index == 3) {
        credit -= readlineSync.questionInt('How much credit would you like to remove? ');
        console.log('This credit has now been removed, your total available credit is: £%d', credit);
    }

    if (index == 0) {
        index = readlineSync.keyInSelect(productList, 'What product would you like?');

        if (index >= 0 && index < products.length) {
            credit -= prices[index];
            console.log('Thank you, your %s has now been dispensed. Your total credit is now £%d', products[index], credit);
        }

        continue;
    }

} while(index != 4);

这里有几个关键的事情，我将解决一些我没看到的问题：

您从未声明index。虽然这在非严格模式下被认为是有效的，但这是不好的做法，因为分配未声明的变量会将其暴露给全局范围。
你没有prices的数组，所以当然你会遇到一些问题，想知道从你的信用中减去什么价值。我冒昧地为你添加了这个阵列。
从价目表中拆分产品列表有利于减少代码的WETness，然后使用array.map函数重建原始列表。
< / LI>
以下是其中的细分：
```
var productList = products.map(function(product, i) {
    return product + ': £' + prices[i];
});
```
此函数遍历products中的值，并为每个值product和每个索引i，它返回一个格式为product: £price的新字符串，存储该字符串到数组productList的相应索引。
1. 我更改了您的console.log语句以使用内联格式化，使其更清晰。 %s表示在此处输入字符串，%d表示在此处输入一个整数。然后使用以下参数填写这些格式说明符。
2. 我在上一个continue块中添加了if语句，以便尽早返回循环。这是因为您选择的产品会覆盖index，因此它不再反映原始菜单选择。

循环中没有保存的整数/部分工作的JS

2 个答案: