怎样做免费网站会员,郑州粒米seo外包,客户管理软件免费版,兰州app开发文章目录 第1章 重构#xff0c;第一个示例1.1 重构前1.2 重构后 第2章 重构原则2.1 何谓重构2.2 两顶帽子2.3 为何重构2.4 何时重构2.5 重构和开发过程 第1章 重构#xff0c;第一个示例
我这里使用的IDE是IntelliJ IDEA
1.1 重构前
plays.js
export const plays {第一个示例1.1 重构前1.2 重构后 第2章 重构原则2.1 何谓重构2.2 两顶帽子2.3 为何重构2.4 何时重构2.5 重构和开发过程 第1章 重构第一个示例
我这里使用的IDE是IntelliJ IDEA
1.1 重构前
plays.js
export const plays {hamlet: {name: Hamlet, type: tragedy},as-like: {name: As You Like It, type: comedy},othello: {name: Othello, type: tragedy}
};invoice.js
export const invoice {customer: BigCo,performances: [{playID: hamlet,audience: 55},{playID: as-like,audience: 35},{playID: othello,audience: 40}]
}statement.js
import {plays} from ./plays.js;
import {invoice} from ./invoice.js;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 creditsvolumeCredits Math.max(perf.audience - 30, 0);// add extra credit for every ten comedy attendeesif (comedy play.type) volumeCredits Math.floor(perf.audience / 5);// print line for this orderresult ${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;
}let res statement(invoice, plays);
console.log(res);package.json
{name: untitled,version: 1.0.0,type: module,dependencies: {}
}运行结果
Statement for BigCoHamlet: $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 credits1.2 重构后
plays.js
export const plays {hamlet: {name: Hamlet, type: tragedy},as-like: {name: As You Like It, type: comedy},othello: {name: Othello, type: tragedy}
};invoice.js
export const invoice {customer: BigCo,performances: [{playID: hamlet,audience: 55},{playID: as-like,audience: 35},{playID: othello,audience: 40}]
}package.json
{name: untitled,version: 1.0.0,type: module,dependencies: {}
}createStatementData.js
class PerformanceCalculator {constructor(aPerformance, aPlay) {this.performance aPerformance;this.play aPlay;}get volumeCredits() {return Math.max(this.performance.audience - 30, 0);}get amount() {throw new Error(subclass responsibility);}
}class TragedyCalculator extends PerformanceCalculator {get amount() {let result 40000;if (this.performance.audience 30) {result 1000 * (this.performance.audience - 30);}return result;}
}class ComedyCalculator extends PerformanceCalculator {get amount() {let result 30000;if (this.performance.audience 20) {result 10000 500 * (this.performance.audience - 20);}result 300 * this.performance.audience;return result;}get volumeCredits() {return super.volumeCredits Math.floor(this.performance.audience / 5);}
}function createPerformanceCalculator(aPerformance, aPlay) {switch (aPlay.type) {case tragedy:return new TragedyCalculator(aPerformance, aPlay);case comedy:return new ComedyCalculator(aPerformance, aPlay);default:throw new Error(unknown type: ${aPlay.type});}
}export function createStatementData(invoice, plays) {const statementData {};statementData.customer invoice.customer;statementData.performances invoice.performances.map(enrichPerformances);statementData.totalAmount totalAmount(statementData);statementData.totalVolumeCredits totalVolumeCredits(statementData);return statementData;function enrichPerformances(aPerformance) {const calculator createPerformanceCalculator(aPerformance, playFor(aPerformance));const result Object.assign({}, aPerformance);result.play calculator.play;result.amount calculator.amount;result.volumeCredits calculator.volumeCredits;return result;}function playFor(aPerformance) {return plays[aPerformance.playID];}function totalAmount(data) {return data.performances.reduce((total, p) total p.amount, 0);}function totalVolumeCredits(data) {return data.performances.reduce((total, p) total p.volumeCredits, 0);}
}statement.js
import {plays} from ./plays.js;
import {invoice} from ./invoice.js;
import {createStatementData} from ./createStatementData.js;function statement(invoice, plays) {return renderPlainText(createStatementData(invoice, plays));
}function renderPlainText(data) {let result Statement for ${data.customer}\n;for (let perf of data.performances) {result ${perf.play.name}: ${usd(perf.amount)} (${perf.audience} seats)\n;}result Amount owed is ${usd(data.totalAmount)}\n;result You earned ${(data.totalVolumeCredits)} credits\n;return result;
}function htmlStatement (invoice, plays) {return renderHtml(createStatementData(invoice, plays));
}
function renderHtml (data) {let result h1Statement for ${data.customer}/h1\n;result table\n;result trthplay/ththseats/ththcost/th/tr;for (let perf of data.performances) {result trtd${perf.play.name}/tdtd${perf.audience}/td;result td${usd(perf.amount)}/td/tr\n;}result /table\n;result pAmount owed is em${usd(data.totalAmount)}/em/p\n;result pYou earned em${data.totalVolumeCredits}/em credits/p\n;return result;
}function usd(aNumber) {return new Intl.NumberFormat(en-US,{style: currency, currency: USD,minimumFractionDigits: 2}).format(aNumber / 100);
}let res statement(invoice, plays);
console.log(res);
let assert_res Statement for BigCo\n Hamlet: $650.00 (55 seats)\n As You Like It: $580.00 (35 seats)\n Othello: $500.00 (40 seats)\n Amount owed is $1,730.00\n You earned 47 credits\nconsole.log(res assert_res)第2章 重构原则
2.1 何谓重构
重构名词在不改变软件可观察行为的前提下提高其可理解性降低其修改成本。
重构动词使用重构手法在不改变软件可观察行为的前提下调整其结构。
重构的过程中代码必须保持可用。如果重构导致代码不可用那么它不可以称之为重构。
重构与性能优化的对比
重构性能优化都修改代码都不改变系统功能都修改代码都不改变系统功能为了可读性为了可扩展性为了提升系统性能
2.2 两顶帽子
添加新功能不应该修改已有代码只关注新功能。增加新测试通过测试衡量工作进度重构只改变程序内部结构不应该添加测试存在遗漏不修改测试除非接口发生变化软件开发在这两者之间切换
2.3 为何重构
改进软件设计程序的设计在没有重构的情况下逐渐腐败变质功能的增加或者修改可能使代码越来越难以理解。软件更容易理解提高代码可读性。帮助找出bug这个是建立在代码容易理解之上的。提高编程速度良好设计降低开发和理解成本。 2.4 何时重构
事不过三三则重构重复性问题若出现三次就应该考虑重构。
见机行事重构
预备性重构最佳时机是在添加新功能之前进行磨刀不误砍柴工。阅读时重构遇到难以理解的代码时考虑是否可以通过重构使其更清晰。人的思考资源宝贵重构就是把理解转移到代码中沉淀知识。捡垃圾式重构“童子军军规”——至少让营地比你来时更干净。
有计划的重构 日常编程中的重构重构应是为了自己而非单独排期。 长期重构大型重构应由整个团队共同参与逐步推进。 CodeReview时的重构考虑他人的理解提高代码和设计的可读性。 添加功能时重构一方面可能是需要理解需要修改的代码另一方面是使增加新特性更加容易。 修补错误时重构出现bug的时候难以找出问题所在的时候很有可能是代码不清晰导致查找bug的困难。
何时不应重构
不需人理解的抽象代码不需人常常修改可放任自流。重写成本低于重构若从头开始更经济无需重构。
2.5 重构和开发过程
重构中不断集成基于主干开发保证自测试用例的完整性CI持续集成、自动化测试和重构是不可分割的三位一体。
