javascript代码简介之道
javascript代码简介之道
来源 https://github.com/ryanmcdermott/clean-code-javascript?utm_source=ESnextNews.com&utm_medium=Weekly+Newsletter&utm_campaign=2017-00-09#variables
目录
- Introduction
- Variables
- Functions
- Objects and Data Structures
- Classes
- Testing
- Concurrency
- Error Handling
- Formatting
- Comments
Introduction
略
Variables
使用有意义的和可推断的变量名
Bad:
const yyyymmdstr = moment().format('YYYY/MM/DD');
Good:
const yearMonthDay = moment().format('YYYY/MM/DD');
对于相同类型的变量使用相同的词汇
Bad:
getUserInfo();
getClientData();
getCustomerRecord();
Good:
getUser();
使用可以搜索的名称
我们读代码的时间会比写代码的时间更长。所以代码一定要 可读 可搜索。 但是未命名的变量会影响理解我们的程序。 使用ESLint 可以帮助识别未命名的常量。
Bad:
// What the heck is 86400 for?
setTimeout(() => {
this.blastOff()
}, 86400);
Good:
// Declare them as capitalized `const` globals.
const SECONDS_IN_A_DAY = 86400;
setTimeout(() => {
this.blastOff()
}, SECONDS_IN_A_DAY);
使用解释性的变量
Bad:
const address = 'One Infinite Loop, Cupertino 95014';
const cityStateRegex = /^[^,\\]+[,\\\s]+(.+?)\s*(\d{5})?$/;
saveCityState(address.match(cityStateRegex)[1], address.match(cityStateRegex)[2]);
Good:
const address = 'One Infinite Loop, Cupertino 95014';
const cityStateRegex = /^[^,\\]+[,\\\s]+(.+?)\s*(\d{5})?$/;
const [, city, state] = address.match(cityStateRegex);
saveCityState(city, state);
避免精神映射
解释性 比 含蓄 好
Bad:
const locations = ['Austin', 'New York', 'San Francisco'];
locations.forEach((l) => {
doStuff();
doSomeOtherStuff();
// ...
// ...
// ...
// Wait, what is `l` for again?
dispatch(l);
});
Good:
const locations = ['Austin', 'New York', 'San Francisco'];
locations.forEach((location) => {
doStuff();
doSomeOtherStuff();
// ...
// ...
// ...
dispatch(location);
});
不要增加不必要的上下文
如果你的 class/object 名称已经告诉你了，就不要在变量名中重复了
Bad:
const Car = {
carMake: 'Honda',
carModel: 'Accord',
carColor: 'Blue'
};
function paintCar(car) {
car.carColor = 'Red';
}
Good:
const Car = {
make: 'Honda',
model: 'Accord',
color: 'Blue'
};
function paintCar(car) {
car.color = 'Red';
}
使用变量默认值 代替 短路判断 或者 条件判断
Bad:
function createMicrobrewery(name) {
const breweryName = name || 'Hipster Brew Co.';
...
}
Good:
function createMicrobrewery(breweryName = 'Hipster Brew Co.') {
...
}
Functions
函数参数数量 (2个或者更少)
限制函数参数数量是意想不到的重要的，因为可以使函数测试起来更容易。超过3个参数将会带来指数级的测试用例增加。 没有参数是最好的情况，一个两个也可以，但是三个以上一定要避免。 通常过多的参数说明你的函数尝试做太多的事情。 如果并不是，那么可以尝试将参数作为对象传递。
Bad:
function createMenu(title, body, buttonText, cancellable) {
// ...
}
Good:
const menuConfig = {
title: 'Foo',
body: 'Bar',
buttonText: 'Baz',
cancellable: true
};
function createMenu(config) {
// ...
}
函数应当只做一件事情
对于软件工程师来说，这是最重要的一点。让函数做更多地事情，将会变得很难撰写，测试，理解。 一个函数固定做一件事情，就可以很容易被重构，和清晰阅读。
Bad:
function emailClients(clients) {
clients.forEach((client) => {
const clientRecord = database.lookup(client);
if (clientRecord.isActive()) {
email(client);
}
});
}
Good:
function emailClients(clients) {
clients
.filter(isClientActive)
.forEach(email);
}
function isClientActive(client) {
const clientRecord = database.lookup(client);
return clientRecord.isActive();
}
函数名应说清它做什么
Bad:
function addToDate(date, month) {
// ...
}
const date = new Date();
// It's hard to to tell from the function name what is added
addToDate(date, 1);
Good:
function addMonthToDate(month, date) {
// ...
}
const date = new Date();
addMonthToDate(1, date);
函数应该只有一层抽象
如果函数有超过一层的抽象，说明它做的事情太多了。 拆分函数作为可复用块。
Bad:
function parseBetterJSAlternative(code) {
const REGEXES = [
// ...
];
const statements = code.split(' ');
const tokens = [];
REGEXES.forEach((REGEX) => {
statements.forEach((statement) => {
// ...
});
});
const ast = [];
tokens.forEach((token) => {
// lex...
});
ast.forEach((node) => {
// parse...
});
}
Good:
function tokenize(code) {
const REGEXES = [
// ...
];
const statements = code.split(' ');
const tokens = [];
REGEXES.forEach((REGEX) => {
statements.forEach((statement) => {
tokens.push( /* ... */ );
});
});
return tokens;
}
function lexer(tokens) {
const ast = [];
tokens.forEach((token) => {
ast.push( /* ... */ );
});
return ast;
}
function parseBetterJSAlternative(code) {
const tokens = tokenize(code);
const ast = lexer(tokens);
ast.forEach((node) => {
// parse...
});
}
移除重复代码
永远，永远，任何情况下，都不要有重复代码。 重复代码意味着你需要一次修改多个地方。 Js是没有类型的，意味着提取通用函数非常容易。 一些工具如 jsinspect 可以帮助你找到重复代码并删除
Bad:
function showDeveloperList(developers) {
developers.forEach((developer) => {
const expectedSalary = developer.calculateExpectedSalary();
const experience = developer.getExperience();
const githubLink = developer.getGithubLink();
const data = {
expectedSalary: expectedSalary,
experience: experience,
githubLink: githubLink
};
render(data);
});
}
function showManagerList(managers) {
managers.forEach((manager) => {
const expectedSalary = manager.calculateExpectedSalary();
const experience = manager.getExperience();
const portfolio = manager.getMBAProjects();
const data = {
expectedSalary: expectedSalary,
experience: experience,
portfolio: portfolio
};
render(data);
});
}
Good:
function showList(employees) {
employees.forEach((employee) => {
const expectedSalary = employee.calculateExpectedSalary();
const experience = employee.getExperience();
let portfolio = employee.getGithubLink();
if (employee.type === 'manager') {
portfolio = employee.getMBAProjects();
}
const data = {
expectedSalary: expectedSalary,
experience: experience,
portfolio: portfolio
};
render(data);
});
}
使用 Object.assign 来设置默认对象
Bad:
const menuConfig = {
title: null,
body: 'Bar',
buttonText: null,
cancellable: true
};
function createMenu(config) {
config.title = config.title || 'Foo';
config.body = config.body || 'Bar';
config.buttonText = config.buttonText || 'Baz';
config.cancellable = config.cancellable === undefined ? config.cancellable : true;
}
createMenu(menuConfig);
Good:
const menuConfig = {
title: 'Order',
// User did not include 'body' key
buttonText: 'Send',
cancellable: true
};
function createMenu(config) {
config = Object.assign({
title: 'Foo',
body: 'Bar',
buttonText: 'Baz',
cancellable: true
}, config);
// config now equals: {title: "Order", body: "Bar", buttonText: "Send", cancellable: true}
// ...
}
createMenu(menuConfig);
不要使用flags 作为函数参数
Flags 告诉你的用户函数可以做多件事情， 函数应当只做一件事情。 如果你的函数根据 if 进入不同的路径，你需要拆分它
Bad:
function createFile(name, temp) {
if (temp) {
fs.create(`./temp/${name}`);
} else {
fs.create(name);
}
}
Good:
function createFile(name) {
fs.create(name);
}
function createTempFile(name) {
createFile(`./temp/${name}`);
}
避免边际效应
如果函数不是接收一个值 并 返回一个值，它就会产生边际效应
Bad:
// Global variable referenced by following function.
// If we had another function that used this name, now it'd be an array and it could break it.
let name = 'Ryan McDermott';
function splitIntoFirstAndLastName() {
name = name.split(' ');
}
splitIntoFirstAndLastName();
console.log(name); // ['Ryan', 'McDermott'];
Good:
function splitIntoFirstAndLastName(name) {
return name.split(' ');
}
const name = 'Ryan McDermott';
const newName = splitIntoFirstAndLastName(name);
console.log(name); // 'Ryan McDermott';
console.log(newName); // ['Ryan', 'McDermott'];
不要直接对全局函数进行修改
Bad:
Array.prototype.diff = function diff(comparisonArray) {
const values = [];
const hash = {};
for (const i of comparisonArray) {
hash[i] = true;
}
for (const i of this) {
if (!hash[i]) {
values.push(i);
}
}
return values;
};
Good:
class SuperArray extends Array {
constructor(...args) {
super(...args);
}
diff(comparisonArray) {
const values = [];
const hash = {};
for (const i of comparisonArray) {
hash[i] = true;
}
for (const i of this) {
if (!hash[i]) {
values.push(i);
}
}
return values;
}
}
尽量使用函数式编程
Bad:
const programmerOutput = [
{
name: 'Uncle Bobby',
linesOfCode: 500
}, {
name: 'Suzie Q',
linesOfCode: 1500
}, {
name: 'Jimmy Gosling',
linesOfCode: 150
}, {
name: 'Gracie Hopper',
linesOfCode: 1000
}
];
let totalOutput = 0;
for (let i = 0; i < programmerOutput.length; i++) {
totalOutput += programmerOutput[i].linesOfCode;
}
Good:
const programmerOutput = [
{
name: 'Uncle Bobby',
linesOfCode: 500
}, {
name: 'Suzie Q',
linesOfCode: 1500
}, {
name: 'Jimmy Gosling',
linesOfCode: 150
}, {
name: 'Gracie Hopper',
linesOfCode: 1000
}
];
const totalOutput = programmerOutput
.map((programmer) => programmer.linesOfCode)
.reduce((acc, linesOfCode) => acc + linesOfCode, 0);
对条件判断进行封装
Bad:
if (fsm.state === 'fetching' && isEmpty(listNode)) {
// ...
}
Good:
function shouldShowSpinner(fsm, listNode) {
return fsm.state === 'fetching' && isEmpty(listNode);
}
if (shouldShowSpinner(fsmInstance, listNodeInstance)) {
// ...
}
避免否定条件判断
Bad:
function isDOMNodeNotPresent(node) {
// ...
}
if (!isDOMNodeNotPresent(node)) {
// ...
}
Good:
function isDOMNodePresent(node) {
// ...
}
if (isDOMNodePresent(node)) {
// ...
}
避免判断
Bad:
class Airplane {
// ...
getCruisingAltitude() {
switch (this.type) {
case '777':
return this.getMaxAltitude() - this.getPassengerCount();
case 'Air Force One':
return this.getMaxAltitude();
case 'Cessna':
return this.getMaxAltitude() - this.getFuelExpenditure();
}
}
}
Good:
class Airplane {
// ...
}
class Boeing777 extends Airplane {
// ...
getCruisingAltitude() {
return this.getMaxAltitude() - this.getPassengerCount();
}
}
class AirForceOne extends Airplane {
// ...
getCruisingAltitude() {
return this.getMaxAltitude();
}
}
class Cessna extends Airplane {
// ...
getCruisingAltitude() {
return this.getMaxAltitude() - this.getFuelExpenditure();
}
}
避免类型检查 (part 1)
JS是无类型的，这意味着可以函数可以接收任何类型的参数。 有时候你担心这种自由而进行类型检查。 有很多方式来避免类型检查 第一个就是考虑一致性APIs
Bad:
function travelToTexas(vehicle) {
if (vehicle instanceof Bicycle) {
vehicle.peddle(this.currentLocation, new Location('texas'));
} else if (vehicle instanceof Car) {
vehicle.drive(this.currentLocation, new Location('texas'));
}
}
Good:
function travelToTexas(vehicle) {
vehicle.move(this.currentLocation, new Location('texas'));
}
避免类型检查 (part 2)
如果使用基础数据类型如 strings numbers ，而又不能进行多态，确实需要类型检查。 应该考虑 TypeScript
Bad:
function combine(val1, val2) {
if (typeof val1 === 'number' && typeof val2 === 'number' ||
typeof val1 === 'string' && typeof val2 === 'string') {
return val1 + val2;
}
throw new Error('Must be of type String or Number');
}
Good:
function combine(val1, val2) {
return val1 + val2;
}
不要过度优化
现代浏览器在运行时进行了大量的优化，完全不需要浪费时间自己进行优化
Bad:
// On old browsers, each iteration with uncached `list.length` would be costly
// because of `list.length` recomputation. In modern browsers, this is optimized.
for (let i = 0, len = list.length; i < len; i++) {
// ...
}
Good:
for (let i = 0; i < list.length; i++) {
// ...
}
移除旧代码
*Bad:**
function oldRequestModule(url) {
// ...
}
function newRequestModule(url) {
// ...
}
const req = newRequestModule;
inventoryTracker('apples', req, 'www.inventory-awesome.io');
Good:
function newRequestModule(url) {
// ...
}
const req = newRequestModule;
inventoryTracker('apples', req, 'www.inventory-awesome.io');
对象和数据结构
使用 getters 和 setters
JavaScript没有接口或者类型，所以很难做到这种模式，因为我们没有 public 和 private。 使用 getters 和 setters 来连接对象数据会比直接查找对象属性会快。
Bad:
class BankAccount {
constructor() {
this.balance = 1000;
}
}
const bankAccount = new BankAccount();
// Buy shoes...
bankAccount.balance -= 100;
Good:
class BankAccount {
constructor(balance = 1000) {
this._balance = balance;
}
// It doesn't have to be prefixed with `get` or `set` to be a getter/setter
set balance(amount) {
if (verifyIfAmountCanBeSetted(amount)) {
this._balance = amount;
}
}
get balance() {
return this._balance;
}
verifyIfAmountCanBeSetted(val) {
// ...
}
}
const bankAccount = new BankAccount();
// Buy shoes...
bankAccount.balance -= shoesPrice;
// Get balance
let balance = bankAccount.balance;
为对象创建私有成员
Bad:
const Employee = function(name) {
this.name = name;
};
Employee.prototype.getName = function getName() {
return this.name;
};
const employee = new Employee('John Doe');
console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe
delete employee.name;
console.log(`Employee name: ${employee.getName()}`); // Employee name: undefined
Good:
const Employee = function (name) {
this.getName = function getName() {
return name;
};
};
const employee = new Employee('John Doe');
console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe
delete employee.name;
console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe
Classes
Single Responsibility Principle (SRP) 单一责任原则
Open/Closed Principle (OCP) 开关原理
Liskov Substitution Principle (LSP) 利斯科夫替代原则
Interface Segregation Principle (ISP) 接口分离原则
Dependency Inversion Principle (DIP) 依赖倒置原则
- 高级模块不应该依赖低级模块。都应该依赖抽象。
- 抽象不应该依赖详细，详细应该依赖抽象。
Bad:
class InventoryRequester {
constructor() {
this.REQ_METHODS = ['HTTP'];
}
requestItem(item) {
// ...
}
}
class InventoryTracker {
constructor(items) {
this.items = items;
// BAD: We have created a dependency on a specific request implementation.
// We should just have requestItems depend on a request method: `request`
this.requester = new InventoryRequester();
}
requestItems() {
this.items.forEach((item) => {
this.requester.requestItem(item);
});
}
}
const inventoryTracker = new InventoryTracker(['apples', 'bananas']);
inventoryTracker.requestItems();
Good:
class InventoryTracker {
constructor(items, requester) {
this.items = items;
this.requester = requester;
}
requestItems() {
this.items.forEach((item) => {
this.requester.requestItem(item);
});
}
}
class InventoryRequesterV1 {
constructor() {
this.REQ_METHODS = ['HTTP'];
}
requestItem(item) {
// ...
}
}
class InventoryRequesterV2 {
constructor() {
this.REQ_METHODS = ['WS'];
}
requestItem(item) {
// ...
}
}
### Prefer ES2015/ES6 classes over ES5 plain functions
**Bad:**
```javascript
const Animal = function(age) {
if (!(this instanceof Animal)) {
throw new Error('Instantiate Animal with `new`');
}
this.age = age;
};
Animal.prototype.move = function move() {};
const Mammal = function(age, furColor) {
if (!(this instanceof Mammal)) {
throw new Error('Instantiate Mammal with `new`');
}
Animal.call(this, age);
this.furColor = furColor;
};
Mammal.prototype = Object.create(Animal.prototype);
Mammal.prototype.constructor = Mammal;
Mammal.prototype.liveBirth = function liveBirth() {};
const Human = function(age, furColor, languageSpoken) {
if (!(this instanceof Human)) {
throw new Error('Instantiate Human with `new`');
}
Mammal.call(this, age, furColor);
this.languageSpoken = languageSpoken;
};
Human.prototype = Object.create(Mammal.prototype);
Human.prototype.constructor = Human;
Human.prototype.speak = function speak() {};
Good:
class Animal {
constructor(age) {
this.age = age;
}
move() { /* ... */ }
}
class Mammal extends Animal {
constructor(age, furColor) {
super(age);
this.furColor = furColor;
}
liveBirth() { /* ... */ }
}
class Human extends Mammal {
constructor(age, furColor, languageSpoken) {
super(age, furColor);
this.languageSpoken = languageSpoken;
}
speak() { /* ... */ }
}
Use method chaining 使用链式方法
Bad:
class Car {
constructor() {
this.make = 'Honda';
this.model = 'Accord';
this.color = 'white';
}
setMake(make) {
this.make = make;
}
setModel(model) {
this.model = model;
}
setColor(color) {
this.color = color;
}
save() {
console.log(this.make, this.model, this.color);
}
}
const car = new Car();
car.setColor('pink');
car.setMake('Ford');
car.setModel('F-150');
car.save();
Good:
class Car {
constructor() {
this.make = 'Honda';
this.model = 'Accord';
this.color = 'white';
}
setMake(make) {
this.make = make;
// NOTE: Returning this for chaining
return this;
}
setModel(model) {
this.model = model;
// NOTE: Returning this for chaining
return this;
}
setColor(color) {
this.color = color;
// NOTE: Returning this for chaining
return this;
}
save() {
console.log(this.make, this.model, this.color);
// NOTE: Returning this for chaining
return this;
}
}
const car = new Car()
.setColor('pink')
.setMake('Ford')
.setModel('F-150')
.save();
Prefer composition over inheritance 组件继承
Bad:
class Employee {
constructor(name, email) {
this.name = name;
this.email = email;
}
// ...
}
// Bad because Employees "have" tax data. EmployeeTaxData is not a type of Employee
class EmployeeTaxData extends Employee {
constructor(ssn, salary) {
super();
this.ssn = ssn;
this.salary = salary;
}
// ...
}
Good:
class EmployeeTaxData {
constructor(ssn, salary) {
this.ssn = ssn;
this.salary = salary;
}
// ...
}
class Employee {
constructor(name, email) {
this.name = name;
this.email = email;
}
setTaxData(ssn, salary) {
this.taxData = new EmployeeTaxData(ssn, salary);
}
// ...
}
Testing
每个测试一个理念
Bad:
const assert = require('assert');
describe('MakeMomentJSGreatAgain', () => {
it('handles date boundaries', () => {
let date;
date = new MakeMomentJSGreatAgain('1/1/2015');
date.addDays(30);
date.shouldEqual('1/31/2015');
date = new MakeMomentJSGreatAgain('2/1/2016');
date.addDays(28);
assert.equal('02/29/2016', date);
date = new MakeMomentJSGreatAgain('2/1/2015');
date.addDays(28);
assert.equal('03/01/2015', date);
});
});
Good:
const assert = require('assert');
describe('MakeMomentJSGreatAgain', () => {
it('handles 30-day months', () => {
const date = new MakeMomentJSGreatAgain('1/1/2015');
date.addDays(30);
date.shouldEqual('1/31/2015');
});
it('handles leap year', () => {
const date = new MakeMomentJSGreatAgain('2/1/2016');
date.addDays(28);
assert.equal('02/29/2016', date);
});
it('handles non-leap year', () => {
const date = new MakeMomentJSGreatAgain('2/1/2015');
date.addDays(28);
assert.equal('03/01/2015', date);
});
});
Concurrency
使用 Promises, 不是 回调
Bad:
require('request').get('https://en.wikipedia.org/wiki/Robert_Cecil_Martin', (requestErr, response) => {
if (requestErr) {
console.error(requestErr);
} else {
require('fs').writeFile('article.html', response.body, (writeErr) => {
if (writeErr) {
console.error(writeErr);
} else {
console.log('File written');
}
});
}
});
Good:
require('request-promise').get('https://en.wikipedia.org/wiki/Robert_Cecil_Martin')
.then((response) => {
return require('fs-promise').writeFile('article.html', response);
})
.then(() => {
console.log('File written');
})
.catch((err) => {
console.error(err);
});
Async/Await 比 Promises 更清晰
require('request-promise').get('https://en.wikipedia.org/wiki/Robert_Cecil_Martin')
.then((response) => {
return require('fs-promise').writeFile('article.html', response);
})
.then(() => {
console.log('File written');
})
.catch((err) => {
console.error(err);
});
Good:
async function getCleanCodeArticle() {
try {
const request = await require('request-promise');
const response = await request.get('https://en.wikipedia.org/wiki/Robert_Cecil_Martin');
const fileHandle = await require('fs-promise');
await fileHandle.writeFile('article.html', response);
console.log('File written');
} catch(err) {
console.error(err);
}
}
Error Handling
不要忽略 catch errors
Bad:
try {
functionThatMightThrow();
} catch (error) {
console.log(error);
}
Good:
try {
functionThatMightThrow();
} catch (error) {
// One option (more noisy than console.log):
console.error(error);
// Another option:
notifyUserOfError(error);
// Another option:
reportErrorToService(error);
// OR do all three!
}
不要忽略 rejected promises
Bad:
getdata()
.then((data) => {
functionThatMightThrow(data);
})
.catch((error) => {
console.log(error);
});
Good:
getdata()
.then((data) => {
functionThatMightThrow(data);
})
.catch((error) => {
// One option (more noisy than console.log):
console.error(error);
// Another option:
notifyUserOfError(error);
// Another option:
reportErrorToService(error);
// OR do all three!
});
Formatting
使用统一的大小写
Bad:
const DAYS_IN_WEEK = 7;
const daysInMonth = 30;
const songs = ['Back In Black', 'Stairway to Heaven', 'Hey Jude'];
const Artists = ['ACDC', 'Led Zeppelin', 'The Beatles'];
function eraseDatabase() {}
function restore_database() {}
class animal {}
class Alpaca {}
Good:
const DAYS_IN_WEEK = 7;
const DAYS_IN_MONTH = 30;
const songs = ['Back In Black', 'Stairway to Heaven', 'Hey Jude'];
const artists = ['ACDC', 'Led Zeppelin', 'The Beatles'];
function eraseDatabase() {}
function restoreDatabase() {}
class Animal {}
class Alpaca {}
函数的调用者和被调用者应靠近
Bad:
class PerformanceReview {
constructor(employee) {
this.employee = employee;
}
lookupPeers() {
return db.lookup(this.employee, 'peers');
}
lookupMananger() {
return db.lookup(this.employee, 'manager');
}
getPeerReviews() {
const peers = this.lookupPeers();
// ...
}
perfReview() {
this.getPeerReviews();
this.getManagerReview();
this.getSelfReview();
}
getManagerReview() {
const manager = this.lookupManager();
}
getSelfReview() {
// ...
}
}
const review = new PerformanceReview(user);
review.perfReview();
Good:
class PerformanceReview {
constructor(employee) {
this.employee = employee;
}
perfReview() {
this.getPeerReviews();
this.getManagerReview();
this.getSelfReview();
}
getPeerReviews() {
const peers = this.lookupPeers();
// ...
}
lookupPeers() {
return db.lookup(this.employee, 'peers');
}
getManagerReview() {
const manager = this.lookupManager();
}
lookupMananger() {
return db.lookup(this.employee, 'manager');
}
getSelfReview() {
// ...
}
}
const review = new PerformanceReview(employee);
review.perfReview();
Comments
只注释有业务逻辑复杂度的东西
Bad:
function hashIt(data) {
// The hash
let hash = 0;
// Length of string
const length = data.length;
// Loop through every character in data
for (let i = 0; i < length; i++) {
// Get character code.
const char = data.charCodeAt(i);
// Make the hash
hash = ((hash << 5) - hash) + char;
// Convert to 32-bit integer
hash &= hash;
}
}
Good:
function hashIt(data) {
let hash = 0;
const length = data.length;
for (let i = 0; i < length; i++) {
const char = data.charCodeAt(i);
hash = ((hash << 5) - hash) + char;
// Convert to 32-bit integer
hash &= hash;
}
}
不要在代码中注释代码
有版本控制工具，让老代码成为历史
Bad:
doStuff();
// doOtherStuff();
// doSomeMoreStuff();
// doSoMuchStuff();
Good:
doStuff();
不要有日记注释
记住，使用版本控制！不需要死代码，注释代码，日志代码。使用 git log 来获取历史！
Bad:
/**
* 2016-12-20: Removed monads, didn't understand them (RM)
* 2016-10-01: Improved using special monads (JP)
* 2016-02-03: Removed type-checking (LI)
* 2015-03-14: Added combine with type-checking (JR)
*/
function combine(a, b) {
return a + b;
}
Good:
function combine(a, b) {
return a + b;
}
避免位置标记
Bad:
////////////////////////////////////////////////////////////////////////////////
// Scope Model Instantiation
////////////////////////////////////////////////////////////////////////////////
$scope.model = {
menu: 'foo',
nav: 'bar'
};
////////////////////////////////////////////////////////////////////////////////
// Action setup
////////////////////////////////////////////////////////////////////////////////
const actions = function() {
// ...
};
Good:
$scope.model = {
menu: 'foo',
nav: 'bar'
};
const actions = function() {
// ...
};
Written on January 12, 2017