clean-code-typescript

Conteúdos

Introdução

Variáveis

Use nomes significantes em suas variáveis

functionbetween<T>(a1:T,a2:T,a3:T){returna2<=a1&&a1<=a3;}

functionbetween<T>(value:T,left:T,right:T){returnleft<=value&&value<=right;}

Use nomes pronunciáveis

classDtaRcrd102{privategenymdhms:Date;privatemodymdhms:Date;privatepszqint='102';}

classCustomer{privategenerationTimestamp:Date;privatemodificationTimestamp:Date;privaterecordId='102';}

Use o mesmo vocabulário para o mesmo tipo de variável

functiongetUserInfo():User;functiongetUserDetails():User;functiongetUserData():User;

functiongetUser():User;

Use nomes fáceis de pesquisar

// What the heck is 86400000 for?setTimeout(restart,86400000);

// Declare them as capitalized named constants.constMILLISECONDS_IN_A_DAY=24*60*60*1000;setTimeout(restart,MILLISECONDS_IN_A_DAY);

Use variáveis explicativas

declareconstusers:Map<string,User>;for(constkeyValueofusers){// iterate through users map}

declareconstusers:Map<string,User>;for(const[id,user]ofusers){// iterate through users map}

Evite mapear mentalmente

constu=getUser();consts=getSubscription();constt=charge(u,s);

constuser=getUser();constsubscription=getSubscription();consttransaction=charge(user,subscription);

Não adicione contextos desnecessários

typeCar={carMake:string;carModel:string;carColor:string;};functionprint(car:Car):void{console.log(`${this.carMake}${this.carModel} (${this.carColor})`);}

typeCar={make:string;model:string;color:string;};functionprint(car:Car):void{console.log(`${this.make}${this.model} (${this.color})`);}

Use argumentos padrões ao invés de encadear condicionais

functionloadPages(count?:number){constloadCount=count!==undefined ?count :10;// ...}

functionloadPages(count:number=10){// ...}

Funções

Argumentos de funções (2 ou menos, idealmente)

functioncreateMenu(title:string,body:string,buttonText:string,cancellable:boolean,){// ...}createMenu('Foo','Bar','Baz',true);

functioncreateMenu(options:{title:string;body:string;buttonText:string;cancellable:boolean;}){// ...}createMenu({title:'Foo',body:'Bar',buttonText:'Baz',cancellable:true,});

typeMenuOptions={title:string;body:string;buttonText:string;cancellable:boolean;};functioncreateMenu(options:MenuOptions){// ...}createMenu({title:'Foo',body:'Bar',buttonText:'Baz',cancellable:true,});

Funções devem fazer somente uma coisa

functionemailClients(clients:Client[]){clients.forEach(client=>{constclientRecord=database.lookup(client);if(clientRecord.isActive()){email(client);}});}

functionemailClients(clients:Client[]){clients.filter(isActiveClient).forEach(email);}functionisActiveClient(client:Client){constclientRecord=database.lookup(client);returnclientRecord.isActive();}

Nomes das funções devem dizer o que elas fazem

functionaddToDate(date:Date,month:number):Date{// ...}constdate=newDate();// It's hard to tell from the function name what is addedaddToDate(date,1);

functionaddMonthToDate(date:Date,month:number):Date{// ...}constdate=newDate();addMonthToDate(date,1);

Funções devem estar em apenas um nível de abstração

functionparseCode(code:string){constREGEXES=[/* ... */];conststatements=code.split(' ');consttokens=[];REGEXES.forEach(regex=>{statements.forEach(statement=>{// ...});});constast=[];tokens.forEach(token=>{// lex...});ast.forEach(node=>{// parse...});}

constREGEXES=[/* ... */];functionparseCode(code:string){consttokens=tokenize(code);constsyntaxTree=parse(tokens);syntaxTree.forEach(node=>{// parse...});}functiontokenize(code:string):Token[]{conststatements=code.split(' ');consttokens:Token[]=[];REGEXES.forEach(regex=>{statements.forEach(statement=>{tokens.push(/* ... */);});});returntokens;}functionparse(tokens:Token[]):SyntaxTree{constsyntaxTree:SyntaxTree[]=[];tokens.forEach(token=>{syntaxTree.push(/* ... */);});returnsyntaxTree;}

Remove código duplicado

functionshowDeveloperList(developers:Developer[]){developers.forEach(developer=>{constexpectedSalary=developer.calculateExpectedSalary();constexperience=developer.getExperience();constgithubLink=developer.getGithubLink();constdata={      expectedSalary,      experience,      githubLink,};render(data);});}functionshowManagerList(managers:Manager[]){managers.forEach(manager=>{constexpectedSalary=manager.calculateExpectedSalary();constexperience=manager.getExperience();constportfolio=manager.getMBAProjects();constdata={      expectedSalary,      experience,      portfolio,};render(data);});}

classDeveloper{// ...getExtraDetails(){return{githubLink:this.githubLink,};}}classManager{// ...getExtraDetails(){return{portfolio:this.portfolio,};}}functionshowEmployeeList(employee:Developer|Manager){employee.forEach(employee=>{constexpectedSalary=developer.calculateExpectedSalary();constexperience=developer.getExperience();constextra=employee.getExtraDetails();constdata={      expectedSalary,      experience,      extra,};render(data);});}

Define objetos padrões utilizando Object.assign ou desestruturação

typeMenuConfig={title?:string;body?:string;buttonText?:string;cancellable?:boolean;};functioncreateMenu(config:MenuConfig){config.title=config.title||'Foo';config.body=config.body||'Bar';config.buttonText=config.buttonText||'Baz';config.cancellable=config.cancellable!==undefined ?config.cancellable :true;}constmenuConfig={title:null,body:'Bar',buttonText:null,cancellable:true,};createMenu(menuConfig);

typeMenuConfig={title?:string;body?:string;buttonText?:string;cancellable?:boolean;};functioncreateMenu(config:MenuConfig){constmenuConfig=Object.assign({title:'Foo',body:'Bar',buttonText:'Baz',cancellable:true,},config,);}createMenu({body:'Bar'});

typeMenuConfig={title?:string;body?:string;buttonText?:string;cancellable?:boolean;};functioncreateMenu({  title='Foo',  body='Bar',  buttonText='Baz',  cancellable=true,}:MenuConfig){// ...}createMenu({body:'Bar'});

Não use flags como parâmetros de funções

functioncreateFile(name:string,temp:boolean){if(temp){fs.create(`./temp/${name}`);}else{fs.create(name);}}

functioncreateFile(name:string){fs.create(name);}functioncreateTempFile(name:string){fs.create(`./temp/${name}`);}

Evite efeitos colaterais (parte 1)

// 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.letname='Robert C. Martin';functiontoBase64(){name=btoa(name);}toBase64();// produces side effects to `name` variableconsole.log(name);// expected to print 'Robert C. Martin' but instead 'Um9iZXJ0IEMuIE1hcnRpbg=='

// 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.constname='Robert C. Martin';functiontoBase64(text:string):string{returnbtoa(text);}constencodedName=toBase64(name);console.log(name);

Evite efeitos colaterais (parte 2)

functionaddItemToCart(cart:CartItem[],item:Item):void{cart.push({item,date:Date.now()});}

functionaddItemToCart(cart:CartItem[],item:Item):CartItem[]{return[...cart,{item,date:Date.now()}];}

Não escreva em funções globais

declare global{interfaceArray<T>{diff(other:T[]):Array<T>;}}if(!Array.prototype.diff){Array.prototype.diff=function<T>(other:T[]):T[]{consthash=newSet(other);returnthis.filter(elem=>!hash.has(elem));};}

classMyArray<T>extendsArray<T>{diff(other:T[]):T[]{consthash=newSet(other);returnthis.filter(elem=>!hash.has(elem));}}

Priorize programação funcional à programação imperativa

constcontributions=[{name:'Uncle Bobby',linesOfCode:500,},{name:'Suzie Q',linesOfCode:1500,},{name:'Jimmy Gosling',linesOfCode:150,},{name:'Gracie Hopper',linesOfCode:1000,},];lettotalOutput=0;for(leti=0;i<contributions.length;i++){totalOutput+=contributions[i].linesOfCode;}

constcontributions=[{name:'Uncle Bobby',linesOfCode:500,},{name:'Suzie Q',linesOfCode:1500,},{name:'Jimmy Gosling',linesOfCode:150,},{name:'Gracie Hopper',linesOfCode:1000,},];consttotalOutput=contributions.reduce((totalLines,output)=>totalLines+output.linesOfCode,0,);

Encapsular condicionais

if(subscription.isTrial||account.balance>0){// ...}

functioncanActivateService(subscription:Subscription,account:Account){returnsubscription.isTrial||account.balance>0;}if(canActivateService(subscription,account)){// ...}

Evite condicionais negativas

functionisEmailNotUsed(email:string){// ...}if(isEmailNotUsed(email)){// ...}

functionisEmailUsed(email){// ...}if(!isEmailUsed(node)){// ...}

Evite condicionais

classAirplane{privatetype:string;// ...getCruisingAltitude(){switch(this.type){case'777':returnthis.getMaxAltitude()-this.getPassengerCount();case'Air Force One':returnthis.getMaxAltitude();case'Cessna':returnthis.getMaxAltitude()-this.getFuelExpenditure();default:thrownewError('Unknown airplane type.');}}}

classAirplane{// ...}classBoeing777extendsAirplane{// ...getCruisingAltitude(){returnthis.getMaxAltitude()-this.getPassengerCount();}}classAirForceOneextendsAirplane{// ...getCruisingAltitude(){returnthis.getMaxAltitude();}}classCessnaextendsAirplane{// ...getCruisingAltitude(){returnthis.getMaxAltitude()-this.getFuelExpenditure();}}

Evite verificação de tipo

functiontravelToTexas(vehicle:Bicycle|Car){if(vehicleinstanceofBicycle){vehicle.pedal(this.currentLocation,newLocation('texas'));}elseif(vehicleinstanceofCar){vehicle.drive(this.currentLocation,newLocation('texas'));}}

typeVehicle=Bicycle|Car;functiontravelToTexas(vehicle:Vehicle){vehicle.move(this.currentLocation,newLocation('texas'));}

Não otimize demais

// On old browsers, each iteration with uncached `list.length` would be costly// because of `list.length` recomputation. In modern browsers, this is optimized.for(leti=0,len=list.length;i<len;i++){// ...}

for(leti=0;i<list.length;i++){// ...}

Remover código morto

functionoldRequestModule(url:string){// ...}functionrequestModule(url:string){// ...}constreq=requestModule;inventoryTracker('apples',req,'www.inventory-awesome.io');

functionrequestModule(url:string){// ...}constreq=requestModule;inventoryTracker('apples',req,'www.inventory-awesome.io');

Use iterators e generators

functionfibonacci(n:number):number[]{if(n===1)return[0];if(n===2)return[0,1];constitems:number[]=[0,1];while(items.length<n){items.push(items[items.length-2]+items[items.length-1]);}returnitems;}functionprint(n:number){fibonacci(n).forEach(fib=>console.log(fib));}// Printa os 10 primeiros números de Fibonnaci.print(10);

// Gera uma corrente infinita de números de Fibonacci.// O generator não mantém um array com todos os números.function*fibonacci():IterableIterator<number>{let[a,b]=[0,1];while(true){yielda;[a,b]=[b,a+b];}}functionprint(n:number){leti=0;for(constfiboffibonacci()){if(i++===n)break;console.log(fib);}}// Printa os 10 primeiros números de Fibonnaci.print(10);

importitiririfrom'itiriri';function*fibonacci():IterableIterator<number>{let[a,b]=[0,1];while(true){yielda;[a,b]=[b,a+b];}}itiriri(fibonacci()).take(10).forEach(fib=>console.log(fib));

Objetos e estruturas de dados

Use getters e setters

classBankAccount{balance:number=0;// ...}constvalue=100;constaccount=newBankAccount();if(value<0){thrownewError('Cannot set negative balance.');}account.balance=value;

classBankAccount{privateaccountBalance:number=0;getbalance():number{returnthis.accountBalance;}setbalance(value:number){if(value<0){thrownewError('Cannot set negative balance.');}this.accountBalance=value;}// ...}constaccount=newBankAccount();account.balance=100;

Fazer objetos ter membros privados/protegidos

classCircle{radius:number;constructor(radius:number){this.radius=radius;}perimeter(){return2*Math.PI*this.radius;}surface(){returnMath.PI*this.radius*this.radius;}}

classCircle{constructor(privatereadonlyradius:number){}perimeter(){return2*Math.PI*this.radius;}surface(){returnMath.PI*this.radius*this.radius;}}

Prefira propriedades de apenas leitura

interfaceConfig{host:string;port:string;db:string;}

interfaceConfig{readonlyhost:string;readonlyport:string;readonlydb:string;}

Classes

Classes devem ser pequenas

classDashboard{getLanguage():string{/* ... */}setLanguage(language:string):void{/* ... */}showProgress():void{/* ... */}hideProgress():void{/* ... */}isDirty():boolean{/* ... */}disable():void{/* ... */}enable():void{/* ... */}addSubscription(subscription:Subscription):void{/* ... */}removeSubscription(subscription:Subscription):void{/* ... */}addUser(user:User):void{/* ... */}removeUser(user:User):void{/* ... */}goToHomePage():void{/* ... */}updateProfile(details:UserDetails):void{/* ... */}getVersion():string{/* ... */}// ...}

classDashboard{disable():void{/* ... */}enable():void{/* ... */}getVersion():string{/* ... */}}// divida as responsábilidades movendo os métodos restantes para outras classes// ...

Classes coesas e desacopladas

classUserManager{// Bad: each private variable is used by one or another group of methods.// It makes clear evidence that the class is holding more than a single responsibility.// If I need only to create the service to get the transactions for a user,// I'm still forced to pass and instance of emailSender.constructor(privatereadonlydb:Database,privatereadonlyemailSender:EmailSender,){}asyncgetUser(id:number):Promise<User>{returnawaitdb.users.findOne({id});}asyncgetTransactions(userId:number):Promise<Transaction[]>{returnawaitdb.transactions.find({userId});}asyncsendGreeting():Promise<void>{awaitemailSender.send('Welcome!');}asyncsendNotification(text:string):Promise<void>{awaitemailSender.send(text);}asyncsendNewsletter():Promise<void>{// ...}}

classUserService{constructor(privatereadonlydb:Database){}asyncgetUser(id:number):Promise<User>{returnawaitdb.users.findOne({id});}asyncgetTransactions(userId:number):Promise<Transaction[]>{returnawaitdb.transactions.find({userId});}}classUserNotifier{constructor(privatereadonlyemailSender:EmailSender){}asyncsendGreeting():Promise<void>{awaitemailSender.send('Welcome!');}asyncsendNotification(text:string):Promise<void>{awaitemailSender.send(text);}asyncsendNewsletter():Promise<void>{// ...}}

Prefira composição à herança

classEmployee{constructor(privatereadonlyname:string,privatereadonlyemail:string){}// ...}// Ruim pois Employees "tem" taxas. EmployeeTaxData não é um tipo de EmployeeclassEmployeeTaxDataextendsEmployee{constructor(name:string,email:string,privatereadonlyssn:string,privatereadonlysalary:number,){super(name,email);}// ...}

classEmployee{privatetaxData:EmployeeTaxData;constructor(privatereadonlyname:string,privatereadonlyemail:string){}setTaxData(ssn:string,salary:number):Employee{this.taxData=newEmployeeTaxData(ssn,salary);returnthis;}// ...}classEmployeeTaxData{constructor(publicreadonlyssn:string,publicreadonlysalary:number){}// ...}

Use cadeia de métodos

classQueryBuilder{privatecollection:string;privatepageNumber:number=1;privateitemsPerPage:number=100;privateorderByFields:string[]=[];from(collection:string):void{this.collection=collection;}page(number:number,itemsPerPage:number=100):void{this.pageNumber=number;this.itemsPerPage=itemsPerPage;}orderBy(...fields:string[]):void{this.orderByFields=fields;}build():Query{// ...}}// ...constquery=newQueryBuilder();query.from('users');query.page(1,100);query.orderBy('firstName','lastName');constquery=queryBuilder.build();

classQueryBuilder{privatecollection:string;privatepageNumber:number=1;privateitemsPerPage:number=100;privateorderByFields:string[]=[];from(collection:string): this{this.collection=collection;returnthis;}page(number:number,itemsPerPage:number=100): this{this.pageNumber=number;this.itemsPerPage=itemsPerPage;returnthis;}orderBy(...fields:string[]): this{this.orderByFields=fields;returnthis;}build():Query{// ...}}// ...constquery=newQueryBuilder().from('users').page(1,100).orderBy('firstName','lastName').build();

SOLID

Principio da única responsabilidade (Single Responsabiliy Principle)

classUserSettings{constructor(privatereadonlyuser:User){}changeSettings(settings:UserSettings){if(this.verifyCredentials()){// ...}}verifyCredentials(){// ...}}

classUserAuth{constructor(privatereadonlyuser:User){}verifyCredentials(){// ...}}classUserSettings{privatereadonlyauth:UserAuth;constructor(privatereadonlyuser:User){this.auth=newUserAuth(user);}changeSettings(settings:UserSettings){if(this.auth.verifyCredentials()){// ...}}}

Prinpio do Aberto/Fechado (Open/Closed Principle)

classAjaxAdapterextendsAdapter{constructor(){super();}// ...}classNodeAdapterextendsAdapter{constructor(){super();}// ...}classHttpRequester{constructor(privatereadonlyadapter:Adapter){}asyncfetch<T>(url:string):Promise<T>{if(this.adapterinstanceofAjaxAdapter){constresponse=awaitmakeAjaxCall<T>(url);// transforma a resposta e retorna}elseif(this.adapterinstanceofNodeAdapter){constresponse=awaitmakeHttpCall<T>(url);// transforma a resposta e retorna}}}functionmakeAjaxCall<T>(url:string):Promise<T>{// faz a requisição e retorna uma Promise}functionmakeHttpCall<T>(url:string):Promise<T>{// faz a requisição e retorna uma Promise}

abstractclassAdapter{abstractasyncrequest<T>(url:string):Promise<T>;}classAjaxAdapterextendsAdapter{constructor(){super();}asyncrequest<T>(url:string):Promise<T>{// faz requisição e retorna uma Promise}// ...}classNodeAdapterextendsAdapter{constructor(){super();}asyncrequest<T>(url:string):Promise<T>{// faz requisição e retorna uma Promise}// ...}classHttpRequester{constructor(privatereadonlyadapter:Adapter){}asyncfetch<T>(url:string):Promise<T>{constresponse=awaitthis.adapter.request<T>(url);// transforma a resposta e retorna}}

Principios da Substituição de Liskov (Liskov Substitution Principle)

classRectangle{constructor(protectedwidth:number=0,protectedheight:number=0){}setColor(color:string){// ...}render(area:number){// ...}setWidth(width:number){this.width=width;}setHeight(height:number){this.height=height;}getArea():number{returnthis.width*this.height;}}classSquareextendsRectangle{setWidth(width:number){this.width=width;this.height=width;}setHeight(height:number){this.width=height;this.height=height;}}functionrenderLargeRectangles(rectangles:Rectangle[]){rectangles.forEach(rectangle=>{rectangle.setWidth(4);rectangle.setHeight(5);constarea=rectangle.getArea();// BAD: Returns 25 for Square. Should be 20.rectangle.render(area);});}constrectangles=[newRectangle(),newRectangle(),newSquare()];renderLargeRectangles(rectangles);

abstractclassShape{setColor(color:string){// ...}render(area:number){// ...}abstractgetArea():number;}classRectangleextendsShape{constructor(privatereadonlywidth=0,privatereadonlyheight=0){super();}getArea():number{returnthis.width*this.height;}}classSquareextendsShape{constructor(privatereadonlylength:number){super();}getArea():number{returnthis.length*this.length;}}functionrenderLargeShapes(shapes:Shape[]){shapes.forEach(shape=>{constarea=shape.getArea();shape.render(area);});}constshapes=[newRectangle(4,5),newRectangle(4,5),newSquare(5)];renderLargeShapes(shapes);

Principio da Segragação de Interface (PSI)

interfaceISmartPrinter{print();fax();scan();}classAllInOnePrinterimplementsISmartPrinter{print(){// ...}fax(){// ...}scan(){// ...}}classEconomicPrinterimplementsISmartPrinter{print(){// ...}fax(){thrownewError('Fax not supported.');}scan(){thrownewError('Scan not supported.');}}

interfaceIPrinter{print();}interfaceIFax{fax();}interfaceIScanner{scan();}classAllInOnePrinterimplementsIPrinter,IFax,IScanner{print(){// ...}fax(){// ...}scan(){// ...}}classEconomicPrinterimplementsIPrinter{print(){// ...}}

Princípio da Inversão de Dependência (DIP) (Dependency Inversion Principle)

import{readFileasreadFileCb}from'fs';import{promisify}from'util';constreadFile=promisify(readFileCb);typeReportData={// ..}classXmlFormatter{parse<T>(content:string):T{// Converts an XML string to an object T}}classReportReader{// BAD: We have created a dependency on a specific request implementation.// We should just have ReportReader depend on a parse method: `parse`privatereadonlyformatter=newXmlFormatter();asyncread(path:string):Promise<ReportData>{consttext=awaitreadFile(path,'UTF8');returnthis.formatter.parse<ReportData>(text);}}// ...constreader=newReportReader();awaitreport=awaitreader.read('report.xml');

import{readFileasreadFileCb}from'fs';import{promisify}from'util';constreadFile=promisify(readFileCb);typeReportData={// ..}interfaceFormatter{parse<T>(content:string):T;}classXmlFormatterimplementsFormatter{parse<T>(content:string):T{// Converts an XML string to an object T}}classJsonFormatterimplementsFormatter{parse<T>(content:string):T{// Converts a JSON string to an object T}}classReportReader{constructor(privatereadonlyformatter:Formatter){}asyncread(path:string):Promise<ReportData>{consttext=awaitreadFile(path,'UTF8');returnthis.formatter.parse<ReportData>(text);}}// ...constreader=newReportReader(newXmlFormatter());awaitreport=awaitreader.read('report.xml');// or if we had to read a json report:constreader=newReportReader(newJsonFormatter());awaitreport=awaitreader.read('report.json');

Testar

As três leis do TDD

Regras F.I.R.S.T

Único conceito por teste

import{assert}from'chai';describe('AwesomeDate',()=>{it('handles date boundaries',()=>{letdate:AwesomeDate;date=newAwesomeDate('1/1/2015');date.addDays(30);assert.equal('1/31/2015',date);date=newAwesomeDate('2/1/2016');date.addDays(28);assert.equal('02/29/2016',date);date=newAwesomeDate('2/1/2015');date.addDays(28);assert.equal('03/01/2015',date);});});

import{assert}from'chai';describe('AwesomeDate',()=>{it('handles 30-day months',()=>{constdate=newAwesomeDate('1/1/2015');date.addDays(30);assert.equal('1/31/2015',date);});it('handles leap year',()=>{constdate=newAwesomeDate('2/1/2016');date.addDays(28);assert.equal('02/29/2016',date);});it('handles non-leap year',()=>{constdate=newAwesomeDate('2/1/2015');date.addDays(28);assert.equal('03/01/2015',date);});});

O nome do teste deve revelar sua intenção

describe('Calendar',()=>{it('2/29/2020',()=>{// ...});it('throws',()=>{// ...});});

describe('Calendar',()=>{it('should handle leap year',()=>{// ...});it('should throw when format is invalid',()=>{// ...});});

Concorrência

Prefira promises à callbacks

import{get}from'request';import{writeFile}from'fs';functiondownloadPage(url:string,saveTo:string,callback:(error:Error,content?:string)=>void,){get(url,(error,response)=>{if(error){callback(error);}else{writeFile(saveTo,response.body,error=>{if(error){callback(error);}else{callback(null,response.body);}});}});}downloadPage('https://en.wikipedia.org/wiki/Robert_Cecil_Martin','article.html',(error,content)=>{if(error){console.error(error);}else{console.log(content);}},);

import{get}from'request';import{writeFile}from'fs';import{promisify}from'util';constwrite=promisify(writeFile);functiondownloadPage(url:string,saveTo:string):Promise<string>{returnget(url).then(response=>write(saveTo,response));}downloadPage('https://en.wikipedia.org/wiki/Robert_Cecil_Martin','article.html',).then(content=>console.log(content)).catch(error=>console.error(error));

Async/Await são ainda mais claros do que Promises

import{get}from'request';import{writeFile}from'fs';import{promisify}from'util';constwrite=util.promisify(writeFile);functiondownloadPage(url:string,saveTo:string):Promise<string>{returnget(url).then(response=>write(saveTo,response));}downloadPage('https://en.wikipedia.org/wiki/Robert_Cecil_Martin','article.html',).then(content=>console.log(content)).catch(error=>console.error(error));

import{get}from'request';import{writeFile}from'fs';import{promisify}from'util';constwrite=promisify(writeFile);asyncfunctiondownloadPage(url:string,saveTo:string):Promise<string>{constresponse=awaitget(url);awaitwrite(saveTo,response);returnresponse;}// somewhere in an async function (Alguma parte de uma função async)try{constcontent=awaitdownloadPage('https://en.wikipedia.org/wiki/Robert_Cecil_Martin','article.html',);console.log(content);}catch(error){console.error(error);}

Tratamento de erros

Sempre use Erro para jogar (throwing) ou rejeitar (rejecting)

functioncalculateTotal(items:Item[]):number{throw'Not implemented.';}functionget():Promise<Item[]>{returnPromise.reject('Not implemented.');}

functioncalculateTotal(items:Item[]):number{thrownewError('Not implemented.');}functionget():Promise<Item[]>{returnPromise.reject(newError('Not implemented.'));}// Ou equivalente a:asyncfunctionget():Promise<Item[]>{thrownewError('Not implemented.');}

typeResult<R>={isError:false;value:R};typeFailure<E>={isError:true;error:E};typeFailable<R,E>=Result<R>|Failure<E>;functioncalculateTotal(items:Item[]):Failable<number,'empty'>{if(items.length===0){return{isError:true,error:'empty'};}// ...return{isError:false,value:42};}

Não ignore erros capturados

try{functionThatMightThrow();}catch(error){console.log(error);}// ou ainda piortry{functionThatMightThrow();}catch(error){// ignorar o erro}

import{logger}from'./logging';try{functionThatMightThrow();}catch(error){logger.log(error);}

Não ignore promises rejeitadas

getUser().then((user:User)=>{returnsendEmail(user.email,'Welcome!');}).catch(error=>{console.log(error);});

import{logger}from'./logging';getUser().then((user:User)=>{returnsendEmail(user.email,'Welcome!');}).catch(error=>{logger.log(error);});// ou usando async/await:try{constuser=awaitgetUser();awaitsendEmail(user.email,'Welcome!');}catch(error){logger.log(error);}

Formatação

Capitalize de forma consistente

constDAYS_IN_WEEK=7;constdaysInMonth=30;constsongs=['Back In Black','Stairway to Heaven','Hey Jude'];constArtists=['ACDC','Led Zeppelin','The Beatles'];functioneraseDatabase(){}functionrestore_database(){}classanimal{}classContainer{}

constDAYS_IN_WEEK=7;constDAYS_IN_MONTH=30;constSONGS=['Back In Black','Stairway to Heaven','Hey Jude'];constARTISTS=['ACDC','Led Zeppelin','The Beatles'];functioneraseDatabase(){}functionrestoreDatabase(){}classAnimal{}classContainer{}

Function callers and callees should be close

Funções que chamam outras funções, ou que são chamadas, devem estar próximas uma das outras.

classPerformanceReview{constructor(privatereadonlyemployee:Employee){}privatelookupPeers(){returndb.lookup(this.employee.id,'peers');}privatelookupManager(){returndb.lookup(this.employee,'manager');}privategetPeerReviews(){constpeers=this.lookupPeers();// ...}review(){this.getPeerReviews();this.getManagerReview();this.getSelfReview();// ...}privategetManagerReview(){constmanager=this.lookupManager();}privategetSelfReview(){// ...}}constreview=newPerformanceReview(employee);review.review();

classPerformanceReview{constructor(privatereadonlyemployee:Employee){}review(){this.getPeerReviews();this.getManagerReview();this.getSelfReview();// ...}privategetPeerReviews(){constpeers=this.lookupPeers();// ...}privatelookupPeers(){returndb.lookup(this.employee.id,'peers');}privategetManagerReview(){constmanager=this.lookupManager();}privatelookupManager(){returndb.lookup(this.employee,'manager');}privategetSelfReview(){// ...}}constreview=newPerformanceReview(employee);review.review();

type vs. interface

interfaceEmailConfig{// ...}interfaceDbConfig{// ...}interfaceConfig{// ...}//...typeShape{// ...}

typeEmailConfig{// ...}typeDbConfig{// ...}typeConfig=EmailConfig|DbConfig;// ...interfaceShape{}classCircleimplementsShape{// ...}classSquareimplementsShape{// ...}

Organize imports

import{TypeDefinition}from'../types/typeDefinition';import{AttributeTypes}from'../model/attribute';import{ApiCredentials,Adapters}from'./common/api/authorization';importfsfrom'fs';import{ConfigPlugin}from'./plugins/config/configPlugin';import{BindingScopeEnum,Container}from'inversify';import'reflect-metadata';

import'reflect-metadata';importfsfrom'fs';import{BindingScopeEnum,Container}from'inversify';import{AttributeTypes}from'../model/attribute';import{TypeDefinition}from'../types/typeDefinition';import{ApiCredentials,Adapters}from'./common/api/authorization';import{ConfigPlugin}from'./plugins/config/configPlugin';

Use alias do typescript

import{UserService}from'../../../services/UserService';

import{UserService}from'@services/UserService';

// tsconfig.json..."compilerOptions":{    ..."baseUrl":"src","paths":{"@services":["services/*"]}...}...

Comentários

Use código que se auto-explica ao invés de comentários

// Checa se subscriptions estão ativas.if(subscription.endDate>Date.now){}

constisSubscriptionActive=subscription.endDate>Date.now;if(isSubscriptionActive){/* ... */}

Não deixe código comentado na sua base de código (codebase)

classUser{name:string;email:string;// age: number;// jobPosition: string;}

classUser{name:string;email:string;}

Não tenha códigos que marcam datas

/** * 2016-12-20: Removed monads, didn't understand them (RM) * 2016-10-01: Improved using special monads (JP) * 2016-02-03: Added type-checking (LI) * 2015-03-14: Implemented combine (JR) */functioncombine(a:number,b:number):number{returna+b;}

functioncombine(a:number,b:number):number{returna+b;}

Evite marcadores posicionados

////////////////////////////////////////////////////////////////////////////////// Client class////////////////////////////////////////////////////////////////////////////////classClient{id:number;name:string;address:Address;contact:Contact;////////////////////////////////////////////////////////////////////////////////// public methods////////////////////////////////////////////////////////////////////////////////publicdescribe():string{// ...}////////////////////////////////////////////////////////////////////////////////// private methods////////////////////////////////////////////////////////////////////////////////privatedescribeAddress():string{// ...}privatedescribeContact():string{// ...}}