Refactoring Improve the design of existing code (version 2), the actual operation of the first example, error: uncaught typeError: invoice.performances is not iterable
1. The troupe stores the data of the play in a simple JSON file.
{
"hamlet": {"name": "Hamlet", "type": "tragedy"},
"as-like": {"name": "As You Like It", "type": "comedy"},
"othello": {"name": "Othello", "type": "tragedy"}
}
2. The bills they issued are also stored in a JSON file.
[
{
"customer": "BigCo",
"performances": [
{
"playID": "hamlet",
"audience": 55
},
{
"playID": "as-like",
"audience": 35
},
{
"playID": "othello",
"audience": 40
}
]
}
]
3. The following simple function is used to print the details of the bill.
function statement(invoice, plays) {
let totalAmount = 0;
let volumeCredits = 0;
let result = `Statement for ${invoice.customer}\n`;
const format = new Intl.NumberFormat("en-US",
{
style: "currency", currency: "USD",
minimumFractionDigits: 2
}).format;
for (let perf of invoice.performances) {
const play = plays[perf.playID];
let thisAmount = 0;
switch (play.type) {
case "tragedy":
thisAmount = 40000;
if (perf.audience > 30) {
thisAmount += 1000 * (perf.audience - 30);
}
break;
case "comedy":
thisAmount = 30000;
if (perf.audience > 20) {
thisAmount += 10000 + 500 * (perf.audience - 20);
}
thisAmount += 300 * perf.audience;
break;
default:
throw new Error(`unknown type: ${play.type}`);
}
// add volume credits
volumeCredits += Math.max(perf.audience - 30, 0);
// add extra credit for every ten comedy attendees
if ("comedy" === play.type) volumeCredits += Math.floor(perf.audience / 5);
// print line for this order
result += ` ${play.name}: ${format(thisAmount / 100)} (${perf.audience} seats)\n`;
totalAmount += thisAmount;
}
result += `Amount owed is ${format(totalAmount / 100)}\n`;
result += `You earned ${volumeCredits} credits\n`;
return result;
}
4. Use the above data files (invoices.json and plays.json) as test input, run this code, you will get the following output:
Statement for BigCo
Hamlet: $650.00 (55 seats)
As You Like It: $580.00 (35 seats)
Othello: $500.00 (40 seats)
Amount owed is $1,730.00
You earned 47 credits
5. Decide to put the data of the data file into the variable, and then print out the running result through the browser console. Create a new html file: statement.html
let invoice = [
{
"customer": "BigCo",
"performances": [
{
"playID": "hamlet",
"audience": 55
},
{
"playID": "as-like",
"audience": 35
},
{
"playID": "othello",
"audience": 40
}
]
}
];
let plays = {
"hamlet": {"name": "Hamlet", "type": "tragedy"},
"as-like": {"name": "As You Like It", "type": "comedy"},
"othello": {"name": "Othello", "type": "tragedy"}
};
function statement(invoice, plays) {
let totalAmount = 0;
let volumeCredits = 0;
let result = `Statement for ${invoice.customer}\n`;
const format = new Intl.NumberFormat("en-US",
{
style: "currency", currency: "USD",
minimumFractionDigits: 2
}).format;
for (let perf of invoice.performances) {
const play = plays[perf.playID];
let thisAmount = 0;
switch (play.type) {
case "tragedy":
thisAmount = 40000;
if (perf.audience > 30) {
thisAmount += 1000 * (perf.audience - 30);
}
break;
case "comedy":
thisAmount = 30000;
if (perf.audience > 20) {
thisAmount += 10000 + 500 * (perf.audience - 20);
}
thisAmount += 300 * perf.audience;
break;
default:
throw new Error(`unknown type: ${play.type}`);
}
// add volume credits
volumeCredits += Math.max(perf.audience - 30, 0);
// add extra credit for every ten comedy attendees
if ("comedy" === play.type) volumeCredits += Math.floor(perf.audience / 5);
// print line for this order
result += ` ${play.name}: ${format(thisAmount / 100)} (${perf.audience} seats)\n`;
totalAmount += thisAmount;
}
result += `Amount owed is ${format(totalAmount / 100)}\n`;
result += `You earned ${volumeCredits} credits\n`;
return result;
}
console.log(statement(invoice, plays));
6. When running, an error is reported: uncaught typeError: Invoice.Performances is not iterable. as shown in Figure 1
Figure 1
Uncaught TypeError: invoice.performances is not iterable
at statement (statement.html:35:28)
at statement.html:71:13
statement @ statement.html:35
（匿名） @ statement.html:71
7. The reason is that Invoice is not an object, but an array. Define the definition of Invoice[]remove. as shown in Figure 2
![原因在于 invoice 并非一个对象，而是一个数组。将 invoice 的定义的 [] 去掉](https://www.shuijingwanwq.com/wp-content/uploads/2022/07/2-5.png)
Figure 2
let invoice = {
"customer": "BigCo",
"performances": [
{
"playID": "hamlet",
"audience": 55
},
{
"playID": "as-like",
"audience": 35
},
{
"playID": "othello",
"audience": 40
}
]
};
let plays = {
"hamlet": {
"name": "Hamlet",
"type": "tragedy"
},
"as-like": {
"name": "As You Like It",
"type": "comedy"
},
"othello": {
"name": "Othello",
"type": "tragedy"
}
};
function statement(invoice, plays) {
let totalAmount = 0;
let volumeCredits = 0;
let result = `Statement for ${invoice.customer}\n`;
const format = new Intl.NumberFormat("en-US",
{
style: "currency", currency: "USD",
minimumFractionDigits: 2
}).format;
for (let perf of invoice.performances) {
const play = plays[perf.playID];
let thisAmount = 0;
switch (play.type) {
case "tragedy":
thisAmount = 40000;
if (perf.audience > 30) {
thisAmount += 1000 * (perf.audience - 30);
}
break;
case "comedy":
thisAmount = 30000;
if (perf.audience > 20) {
thisAmount += 10000 + 500 * (perf.audience - 20);
}
thisAmount += 300 * perf.audience;
break;
default:
throw new Error(`unknown type: ${play.type}`);
}
// add volume credits
volumeCredits += Math.max(perf.audience - 30, 0);
// add extra credit for every ten comedy attendees
if ("comedy" === play.type) volumeCredits += Math.floor(perf.audience / 5);
// print line for this order
result += ` ${play.name}: ${format(thisAmount / 100)} (${perf.audience} seats)\n`;
totalAmount += thisAmount;
}
result += `Amount owed is ${format(totalAmount / 100)}\n`;
result += `You earned ${volumeCredits} credits\n`;
return result;
}
console.log(statement(invoice, plays));
8. The output is in line with expectations, and no errors will be reported. as shown in Figure 3
Figure 3
Statement for BigCo
Hamlet: $650.00 (55 seats)
As You Like It: $580.00 (35 seats)
Othello: $500.00 (40 seats)
Amount owed is $1,730.00
You earned 47 credits
![在 Python 3 中执行 sys.argv[1] 时，报错：IndexError: list index out of range](https://www.shuijingwanwq.com/wp-content/uploads/2022/10/1-4-520x144.png)
