图3
1、在学习重构：改善既有代码的设计 (第2版)时，发现函数 statement 在末尾缺少1个 }，进而导致代码格式显示上存在问题。如图1
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) {
let thisAmount = amountFor(perf
, playFor(perf)
);
// add volume credits
volumeCredits += Math.max(perf.audience - 30, 0);
// add extra credit for every ten comedy attendees
if ("comedy" === playFor(perf).type) volumeCredits += Math.floor(perf.audience / 5);
// print line for this order
result += ` ${playFor(perf).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;
2、一直误以为是代码本身漏写了 }，不得不自行补充上。最终的程序实现如下
<script>
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 playFor(aPerformance) {
return plays[aPerformance.playID];
}
function amountFor(aPerformance) {
let result = 0;
switch (playFor(aPerformance).type) {
case "tragedy":
result = 40000;
if (aPerformance.audience > 30) {
result += 1000 * (aPerformance.audience - 30);
}
break;
case "comedy":
result = 30000;
if (aPerformance.audience > 20) {
result += 10000 + 500 * (aPerformance.audience - 20);
}
result += 300 * aPerformance.audience;
break;
default:
throw new Error(`unknown type: ${playFor(aPerformance).type}`);
}
return result;
}
function volumeCreditsFor(aPerformance) {
let result = 0;
result += Math.max(aPerformance.audience - 30, 0);
if ("comedy" === playFor(aPerformance).type) result += Math.floor(aPerformance.audience / 5);
return result;
}
function usd(aNumber) {
return new Intl.NumberFormat("en-US",
{
style: "currency", currency: "USD",
minimumFractionDigits: 2
}).format(aNumber / 100);
}
function totalVolumeCredits() {
let result = 0;
for (let perf of invoice.performances) {
result += volumeCreditsFor(perf);
}
return result;
}
function totalAmount() {
let result = 0;
for (let perf of invoice.performances) {
result += amountFor(perf);
}
return result;
}
function statement(invoice, plays) {
let result = `Statement for ${invoice.customer}\n`;
for (let perf of invoice.performances) {
result += ` ${playFor(perf).name}: ${usd(amountFor(perf))} (${perf.audience} seats)\n`;
}
result += `Amount owed is ${usd(totalAmount())}\n`;
result += `You earned ${totalVolumeCredits()} credits\n`;
return result;
}
console.log(statement(invoice, plays));
</script>
3、在 1.5 进展：大量嵌套函数 重构至此，是时候停下来欣赏一下代码的全貌了。发现 函数 statement 的 } 竟然是存在的，只不过由于其中包含了一些嵌套函数，由于并非全貌，因此，并未显示出来。如图2
4、最终决定使用嵌套函数，仍然可以正常运行。如图3
<script>
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 result = `Statement for ${invoice.customer}\n`;
for (let perf of invoice.performances) {
result += ` ${playFor(perf).name}: ${usd(amountFor(perf))} (${perf.audience} seats)\n`;
}
result += `Amount owed is ${usd(totalAmount())}\n`;
result += `You earned ${totalVolumeCredits()} credits\n`;
return result;
function totalAmount() {
let result = 0;
for (let perf of invoice.performances) {
result += amountFor(perf);
}
return result;
}
function totalVolumeCredits() {
let result = 0;
for (let perf of invoice.performances) {
result += volumeCreditsFor(perf);
}
return result;
}
function usd(aNumber) {
return new Intl.NumberFormat("en-US",
{
style: "currency", currency: "USD",
minimumFractionDigits: 2
}).format(aNumber / 100);
}
function volumeCreditsFor(aPerformance) {
let result = 0;
result += Math.max(aPerformance.audience - 30, 0);
if ("comedy" === playFor(aPerformance).type) result += Math.floor(aPerformance.audience / 5);
return result;
}
function playFor(aPerformance) {
return plays[aPerformance.playID];
}
function amountFor(aPerformance) {
let result = 0;
switch (playFor(aPerformance).type) {
case "tragedy":
result = 40000;
if (aPerformance.audience > 30) {
result += 1000 * (aPerformance.audience - 30);
}
break;
case "comedy":
result = 30000;
if (aPerformance.audience > 20) {
result += 10000 + 500 * (aPerformance.audience - 20);
}
result += 300 * aPerformance.audience;
break;
default:
throw new Error(`unknown type: ${playFor(aPerformance).type}`);
}
return result;
}
}
console.log(statement(invoice, plays));
</script>